Don’t bother spending a lot of time and effort on a cool Twitter background. People viewing via a netbook or mobile device either can’t see it, or it’s compressed. If you’re going to make one, look at the design on a small monitor to see what actually shows up.
And don’t forget your profile info in Twitter itself. That’s the first thing I look at when I’m trying to decide whether or not to follow someone (especially on this small screen that requires me to take my fingers off their hard-won position on the tiny little home row and scroll down to be able to see much of anything.)
That info also shows up when you mouse over a Twitter username in your follower list, so that can be just as valuable, if not more, than what you put in the sidebar of a background.
Take a look at your photo, too. People may well be looking at that on a tiny screen. Is your photo tight enough that people can make out your face? How will it look if someone is viewing it on a mobile device and it’s roughly a centimeter square?
I’ve also learned that you should test drive any potential netbook for at least half an hour before buying, because this itty bitty keyboard is still driving me nuts.