Definitely non-flash and preferably non-gif. Possibly HTML5, which is something that looks interesting but which I don't really have any particular need for. And if I don't have a project, I'm probably not going to make time to learn it.

Mostly I was thinking of things like an occasional falling leaf or blossom, or a shooting star in a night starscape, or a fish swimming by in the header. Things that are simple and doable for my minimal art skills.