Just because software is free, does not mean you can't get incredible results out of it. Blender is a free 3D program that has a ton of capabilities, and it has helped create a few movies so far, including the completely open source live action film Tears of Steel. If you've done a bit of 3D work (or if you're brand new to the 3D world), and you've wanted to create some of your own textures, the tutorial below from Cgtuts+ can help you get started.
Here's a preview of the tutorial:
Be sure to head on over to Cgtuts+ for more excellent tutorials that can help you get started working in 3D.