The undead inhabitants of Castle Meatgrinder consist mainly of skeletons from 15mm.co.uk. These are really sharp figures that their website just doesn't do justice. You'll want to check out the big versions of these pictures, these smaller icons lose a lot of their character.
Just zombies and skeletons makes the tomb level of Castle Meatgrinder pretty weak sauce, but the leveling rate of Moldvay Basic is pretty slow, so there will be plenty of time to add in mummies, wraiths, and other fun ghastly things later.
The death cult pack of figures from Rap Partha Europe also includes these three zombie looking fellows. Since the cult in Castle Meatgrinder is dedicated to the dungeongod and not necessarily to any sort of necromancy, it made more sense to me to throw these into the tomb with the above.