I've been searching for three days and can't find anything.

That is very specific. Does it need to be 32x32? What monsters are you looking for(zombies, slimes, etc)

It must be at least 32x32. All generic, not childish monsters which you find in most of the mmorpgs like rats, bugs, slimes, scoprions, zombies, skeletons, dragons, etc. I guess I will need to hire a designer.