Here is something I have found a while ago to help come up with characters or backgrounds for animations,artworks, as well for 3D works as well.
Alchemy lets you brainstorm idea's visually to explore an expanded range of ideas and possibilities in a serendipitous way.
This program for free to use and works on mac and pc and doesn't take up allot of space on your computer.
its suggested to have a tablet for this if not its ok to do without one
Just start messing around with the features such as splatter, randomize, etc there is no wrong way of using it.
Use your imagination look at it and figure out what certain patterns could be(example of this would be like looking at clouds and guessing what they look like).
if it helps pick a theme or subject before finding what shapes look like what
here are some examples of what people have come up with
you can check out the forums to see others examples as well as tips to use it
I'm trying out the program but can't get anything to look like people or animals
I can't either though some will be able to and other can't if you can draw well enough with it you can still get prop idea's or designs out of the program you can apply to your drawings and animations.
Cool program can I use it for anything else
You can save out the images you make in certain formats and bring them into programs such as photoshop,gimp,flash, and even use it to make stencil for 3D sculpting programs like Z-brush,mudbox or Sculptris( free as well http://www.sculptris.com/)