Blue Sky Studios (Ice Age, Robots) have a weekly themed design challenge for all Blue Sky employees to draw/sketch/paint characters of various themes which include:
http://bsschallenge.blogspot.com/200...ite-pixar.html
One of my favorites:

Some very creative and artistic people there.
Here is a link to the main page.
http://bsschallenge.blogspot.com/
- Classic Movie Monsters
- Animal Hybrids
- Muppet Babies
- Dinosaurs!
- Favorite 80's cartoon
- Fairy Tales
- SpongeBob Squarepants
- Winter
http://bsschallenge.blogspot.com/200...ite-pixar.html
One of my favorites:

Some very creative and artistic people there.
Here is a link to the main page.
http://bsschallenge.blogspot.com/