So, one question I had was: what is canvas good for? Ultimately you can draw anything you want, and then use it as an image. I thought, I have my bouncing ball, but it could be drawn with canvas, right? So you could quickly customize your avatar.
This is pretty basic -- it depends on draw/fill/stroke commands for canvas (not that images couldn't be done, however). The color picker is one I found online, and is servicable.