I've recently become addicted to deviantART. Don't misinterpret, I have basically zero illustrating talent, I'm there purely to enjoy the awesome art that people put out. During one of my periodic searches I came across this MINDBLOWINGLY AWESOME piece of ROM art!
It was done by Andrew Griffith, aka glovestudios on deviantART. One of the great things about the deviantART community is that most people don't watermark their stuff or inhibit your ability to download their artwork (there's actually a "download" button). I'm currently using this bad boy as the wallpaper on my Droid phone, and it is beautiful.
So check out deviantART, you'll be amazed at what you can find!