I found this picture while stumbling along StumbleUpon and have seen a good amount of artists on DeviantArt working on this challenge and I absolutely loved the idea, so I figure I wanted to try this. It's a great way to keep the artistic mind flowing and ease one's way out of an art block.
100 Themes Challenge
This one is a good deal more difficult than the 30 Days challenge. A list of 100 themes was created and for each of those themes you must complete a drawing related to said theme. You can find the list here.
Any interesting art challenges you come up with or find, please let me know and I'll post it up here, try to complete it, and put up a link to you as well! :D
