Laptop sleeves are inexpensive enough that you can go ahead and get a new one and not break the bank. Since they usually go inside another bag, you can get a more fun design than you'd normally pick.
Joyrich has a couple of edgy printed sleeves that I'm loving for Fall. The Numero Sleeve ($45) has a cool, typeset-style pattern and fits up to a 17-inch laptop. I also like their Ching a Ling Sleeve ($50), which is a little more street but rad-looking just the same.