For Those Who Aren't Afraid of Permanence
Skins and stickers can make a laptop look cheap. If you have a design in mind--and no issues with voiding your warranty--you can achieve a pretty cool look with laser engraving. [[xref:http://www.adafruit.com/laser/|Adafruit Industries|Adafruit Industries]], an etching service in New York City, charges just US$100 to burn a permanent image onto a laptop case.
(Image from [[xref:http://www.zedomax.com/|Zedomax|Zedomax]].)