I picked up a new phone a few months ago. I got the Sony Ericsson T68i. It's a great little phone and I like it a lot. One issue is that there's so many things it can do that I still haven't gotten around to learning everything. Last night a friend of mine told me about a page with themes for my phone. You can basicly download graphics sets that become the default backgrounds. I chose the Trigun one from this page.
Now I've got all these ideas to make my own themes (hmm, maybe a chobits one...). The site even has tips on making your own themes.