An alright start. I hope you don't plan on using the blue Windows XP bar in your theme though! It's ugly and wouldn't work on Vista or Windows 7.
It's not that hard to create a background for your theme.
That is from TiberiumWeb. You can do a million things with it. Hell, even resize it to 1280x1024 or something and just see how it looks by itself, might look cool! Maybe somebody would be nice enough to make it really pretty for you I however don't have the time at the moment.
Keep us posted man, I'm willing to host it for you on the site.