The contents of tomb will vary from age to age, and person to person. Most will have a small horde of jewelry and wealth, if the tomb hasn't been plundered. The wine, if any, might still be good or vinegar. The dead will be decked out in finery and beautiful weapons. But this all hinges on whether the tomb has been plundered or the weather and time haven't opened the tombs to the air above.
The most common monsters to find are mummies, skeletons, guardian skeletons, golems and wights. One can always scale the undead to their group. It might even be fun to have a curse put on anyone who opens a tomb, (magical which can be dispelled in the normal means, but you might add in a hard way to get it done).