I decided there will be 3 'factions' in the dungeon I will run. Here's the scrapbook for stocking it.
The Good
maxarkes.deviantart.com
The Bad
windmaker.deviantart.com
I have no idea, who drew the last image, but I love how he/she/it made the lizard men look like slavers from some empire, rather than cavemen!
The Goblin
I always really liked the art direction Magic: The Gathering took with portraying goblins, especially in earlier editions. They can be zany, scary, serious and simply stupid, but somehow there is a feeling of an overarching theme that makes them memorable.
Also, while looking for the links to the MtG images, I found a newer card called Goblin Battle Jester. I don't care about the artwork, but the idea of 'battle jesters' is here to stay.