I've started writing up a few ideas. Here are a few monsters, to start with.
HD 2, AC 8, Att: bronze dagger (1d4) or curse, Mv 120’ (40’), Ml 10, Al LE, XP 29
Fanatics of the snake-cult who swore to protect the temple in death as in life. Their ritualistically scarred bodies have been preserved by magic and lain to rest wrapped in golden silks (worth 25gp, if undamaged). The lingering spirits of these men and women will be awoken to avenge any who disturb their rest.
Curse: upon rising, a snake-cult zombie may pronounce a curse upon intruders. The curse affects one target whom the zombie lays eyes upon as it wakes. The target must save versus spells or tremble with fear, incurring a -2 penalty to attacks and a 25% chance of spell failure for 1d6 turns.
HD 4, AC 7, Att: gaze or bronze scimitar (1d6) + constriction (2d4), Mv 120’ (40’), Ml 10, Al LE, XP 190
Female aspirants selected for their sensuous beauty and ruthless devotion to the cult. In life, they were initiated in the secret rites of the priestesses, becoming semi-ophiomorphs -- their eyes and tongues are those of snakes and, in place of legs, they move upon great serpentine tails (10’ long). Finally, they were ritually impaled to bring about a state of lingering undeath. They now serve as sleepless guardians of precious treasures.
Gaze: one whom a snake-priestess zombie focuses her gaze upon must save versus spells. Failure indicates that visions of writhing serpents cause the victim’s will to be overcome. One thus afflicted becomes a mind-slave of the priestess, following her mental commands. Another saving throw is allowed, each time the victim suffers damage. If the snake-priestess dies, any under her command fall unconscious for 1d6 turns.
Constriction: using her great tail, a snake-priestess zombie may grab and constrict a victim. Once an attack with the tail succeeds, the victim is grappled and suffers automatic damage (2d4) each round, as well as a -2 penalty to attack rolls.
Temple Guard Zombie
HD 4+3, AC 5 (bronze plate), Att: bronze broadsword (1d8) + bite (1d8 + poison), Mv 120’ (40’), Ml 10, Al LE, XP 215
Warrior temple guards whose tattooed bodies have been preserved by magic to watch over tombs and shrines of the serpent cult for all eternity. During life, these men underwent a process of physical transformation via dark rituals, gaining deadly, snake-like fangs.
Poison: one bitten by a guardian zombie of the snake-cult must save versus poison or suffer one hit point of damage per turn. The poison lasts indefinitely, until it is neutralised or the victim dies. (Poison from multiple bites is not cumulative.)