I've said this before. One of the advantages of the Pixar/Disney alliance, is they (the artists) can experiment on certain aspects of the cgi procesd. I believe they did this with Tangled which was on the level (visual-wise) of a Pixar film. We have to keep in mind every Pixar film is only made to challenge the artists, to see what they can push.
Bugs Life- nature
Finding Nemo- underwater, sea life
Toy Story 3- aging toys
Monsters Inc- Sully's hairy body
Incredibles- aging humans, and human hair
Cars- chrome, reflection, speed, dirt on metallic surfaces
Wall-E- outer space, more aging earth products and dirty surfaces
Up- Balloons, aging human
Ratatouille- more hair, food