I stumbled across an awesome write-up on CGHub.com discussing the art direction for "Orcs Must Die!" by Robot Entertainment. I've always loved the art books that accompany the uber-level ultimate editions of games, mostly because they let you see what everything looked like before it was so damn shiny, and this post offers similar insights. In David Kubalak's post, he talks about how the art direction changed for OMD mid-course when the development team was designing some of the game's traps.
We explored things like a cardboard cutout of your mage with bombs behind him; blades shooting out of the wall, exploding several orcs into a shower of blood and giblets; and spring traps that send guys ragdolling through the air. All of these ideas had us taking a lighter approach to the game, and then had us thinking if we should do the same with the look and the tone.
Below is an image visually describing this transformation: the orc and ogre images on the left were done before the change in stylization -- notice the exaggerated features of the versions on the right. This tone change really helped sell this concept. This game just can't be taken seriously -- I mean, you're mowing down/crushing/burning piles of baddies.