I'm not going to lie -- I've always thought notebooks with customised covers look slightly pretentious and/or creepy. But if you do fancy having your own artwork emblazoned on your PC, then a contest Dell is currently running might be of interest.
The Make It Yours competition offers up a Dell Studio notebook and $5,000 in cold, hard cash as the prize. As seems de rigeur these days, the winner is being decided by public vote, so get your entry in well ahead of the January 20 date so you can start hassling friends, relatives and social networking acquaintances to vote for you. (Note to Senator Conroy: nudity and "sexually suggestive imagery" are out, so you probably don't need to block this one, OK?)