d100 Petty Undead

Petty undead are the sort that don't cause most adventurers problems but might ad a bit of colour. For low level or zero level you might make them fill a whole adventure. Possibly just hopping around a necromancer lab or in a tainted graveyard. Some might come from funeral urns or canoptic jars. Good for grisly Reanimator action.

Basic Stats
Most have only a d4 HP
Armour as a unarmoured person +1d4
Some with * symbol require silver, cold iron, normal fire or magical item to harm
Some have no attack or only inflict a d2 or d3 or most often d4
All can see in the dark and sense life

d100 Petty Undead
01 Phantom head* - severed non corporeal phantom head appears mouths silent words
02 Moaning head - severed zombie head which comes to life when living hears and moans
03 Chattering skull - when disturbed hops about biting anything alive in sight, often in set
04 Foul Cranium - soft squishy rotten head that spits diseased phlegm at living in sight
05 Fire Skull - a flaming screeching flying skull that illuminates and guards dungeon06 Slime Skull - if disturbed by life will vomit a yard wide pool of acid every round in front
07 Laughing Head* - a form of phantom head but laughs with jollity if disturbed by living
08 Drowned Hand - blue rotten waterlogged severed hand that leaves a dripping trail
09 Clutching Hand - zombie hands left in high places that drop onto victims and grip them
10 Grasping Hand - crawling hand sneaks on sleeping and resting victims to strangle
11 Flaming Hand - floating burning phantom hand that tries to set alight victims
12 Pugilistic Fist - floating zombie fists punch victims often appear in groups
13 Jilted Hand - from a spurned suicidal lover, attacks opposite gender especially with rings
14 Spectral Claw* - floating glowing phantom hands reach inside victims body
15 Rending Fist - skinless swollen hand that tries to batter self into victims body
16 Putrid Claw - rotting slimy hand that touches
17 Wizards Claw - wizened hand covered with tatoos can cast a d5 zero lv Wizard spells
18 Mummy's Hand - bandaged desiccated hand that crawls and drains moisture from living
19 Wraith Hand - a shadowy phantom hand that drains life on touch
20 Plague Hand - crawling pox marked hand, touch drains a CHA point, week/point recover 
21 Bloody Torso - limbless and headless torso that hops and bashes living victims
22 Hungry Torso - ribs open like a horrible mouth and intestines drag victim inside
23 Angry Bones - a collection of loose skeletal parts that hurl themselves at victims
24 Shambling Gore - dripping mound of ground flesh and bones that crushes victims
25 Shambling Eyes - mass of all seeing eyeballs, try and force selves inside a victim
26 Tongue Fiend - mass of crawling tongues that attempt to grapple then smother victim 
27 Gut Buster - animated intestines that strangle and spray stomach acid
28 Gutsack Horror - floating digestive tract, floats or bites or grapples, explodes on death
29 Gastric Fiend - floating gas filled stomach with eyes sprays acid or stinking gas 
30 Hopping Fiends - these hopping purple legs kick intruders, usually found in heaps
31 Scalp Horror - a collection of scalps with animated hair tries to strangle victims
32 Shambling Ash -  mound of cremation ash which can blind and choke victims
33 Stabbing Fiends - arms or legs with sharp bone protruding from stump used to stab
34 Phantom Heart* - non corporeal heat beats loudly when living come near inducing fear
35 Bloody Heart - horrible hopping bloody gristle that tries to enter bodies of the living
36 Clotted Horror - animated pool of blood that leaches victims blood to increase mass 
37 Shadow Heart* - non corporeal shadow that eats light & attacks with tendrils of darkness 
38 Putrid Heart - this crawling slimy horror attacks with strangling diseased arteries
39 Orphan's Teeth - a mass of rotten teeth that crawls and gnaws living things
40 Grey Horror - undead brains that drip acid and crawl like slugs to drop from above
41 Beggar Bones - a crawling crippled skeleton with useless deformed legs
42 Crawling Carcass - zombie human body cut off at waist leaving a trail of rotten goop 
43 Zombie Baby - these horrors often crawl in city sewers, they can leap and bite
44 Zombie Orphan - these undead feral children usually attack in a pack but flee if losing  
45 Spectral Baby*- phantom babies cause fear with a touch and can bite
46 Spectral Orphan* - lost children cause fear with a gaze or can drain blood by touch 
47 Skulk Claws - joined skull, shoulders and arms, attack with a two scratching claws
48 Torso Apparition* - glowing and bloated phantom from waist up, bites and grabs
49 Bloated Carcass - pulsing torso sack full of gas, explodes with stinking or diseased gas
50 Skull Snake - skull with spinal column which crawls and bites
51 Zombie Rat Ball - a group of slowly crawling ferocious rats with fused tails
52 Death Rat - a undead giant rat, as a giant rat but with undead abilities
53 Death Dog - a undead stray street dog, often found in graveyards feeding on dead
54 Gore Hound - skinless savage dog fights as a berserk in negative HP
55 Puss Hound - white dripping stinking undead dog with a diseased bite
56 Bone Dog - these suddenly leap from piles of bones assembling into skeleton dogs
57 Phantom Dog* - these spectral hounds howl by night and leap through people to attack 
58 Necro Owl - evil owls attack those visiting graves with flesh shredding claws 
59 Spectral Owl* - phantom owls can turn invisible and claws ignore non magic armour
60 Nightmare Owl* these shadowy owls call a victims name instilling fear
61 Ghost Fish* - especially hate fishermen, swim through air or through flesh to drain life
62 Necro Fish - undead fish dwell in water of all kinds and can jump to bite those on land
63 Snake Skeleton - these bone snakes can bite or stab with their tails and crawl quickly
64 Nerve Snake - forms from spinal nerve tissue, bite causes ghoul like paralysis
65 Putrid Worm - rotten slimy snakes that can spit acid, leave stinking trails 
66 Sting Worm - these horrid snakes have a bite and paralyzing tail stinger
67 Shadow Cat* - can run through walls and attack by ambush with life draining touch
68 Crypt Cat - seemingly normal cat but up close can see fatal wounds, fierce and sneaky
69 Phantom Cat* - follows loudly screeching, blinks away if attacked, bites from ambush
70 Mummy Cat* - desiccated, bandaged and often bejeweled cats cause disease by bite
71 Shadow Rabbit* - bring dread to rabbits but will attack humans with shadow touch
72 Necro Hare - hopping evil terrors can be seen dancing by night, jump and bite
73 Grave Squirrel - big black rodents that rob graves for flesh, often attack in packs
74 Slime Squirrel - wet stinking critters leap at foes then explode into a small stinking cloud
75 Grave Hog - deadly grave flesh feasting hedgehogs shoot bony spurs often from cover
76 Grave Toad - large toads are former necromancer familiars, bite and know d4 cantrips
77 Shadow Bat - shadowy creatures fly through corporeal bodies and drain life force
78 Blood Bat - skinless bats that drip blood and attach selves to victims to drain blood
79 Stench Bat - putrid bats leave a trail of stinking odor behind them to bite those overcome 
80 Bone Beaver - builds dam from bones dug from graves for material, bite or slap attack
81 Gore Beaver - builds dams from corpses to collect pools of blood, bite or slap attack
82 Doom Drake - black and grey ducks that attack in flocks
83 Night Raven - undead ravens some mutter abusive phases when they attack with pecks
84 Necro Bee Swarm - nocturnal bees make evil honey potions & guard them from thieves 
85 Necro Termite Swarm - Mostly build hives and at wood but can attack from below
86 Necro Crab - a undead crab from the deep, can grapple or nip 2/round,+1 on right claw 
87 Necro Ants Swarm - great diggers can attack from below and some kinds can fly
88 Necro Locust Swarm - eat every bit of meat they can find, and skeletonise the living
89 Necro Wasp Swarm - dwell in evil hive, victims killed arise as zombies
90 Hell Fleas - these are just like blood sucking fleas but normal treatments don't stop them
91 Protoplasmic Horror - gelatinous mass of necrotic organic matter that crushes living
92 Ectoplasmic Fiend* - slimy mass from beyond crushes victim, carries dead to other plane
93 Miasmic Cloud - a stinking vapour that spreads disease but flees any threat
94 Shadow Mist* - a small shadow being that lurks in shadows and drains life away
95 Putrescent Slime - a rotten mass of dead tissue surrounded by stinking gas cloud 
96 Proto Phantom* - remains of a unborn soul with no distinct features that drains life
97 Shroud Phantom* - glowing sheet phantom with a chilling touch, has no memory of past 
98 Screaming Phantom* - translucent human dressed as burial, scream causes fear
99  Grave Phantom* - translucent human dressed as burial, attacks if had a weapon
100 Jack-o-evil* - flying carved pumpkin stuffed with human brains, shoots sparks from eyes

Some references here to undead insect magic a rare specialization for necromancers. They keep queens alive and nurture eggs and larvae then make them undead when hatch into adult stage. In past they made great hives towers and were known as feared Insect wizards. In human times their magic has become less known.