How about putting a plastic winged gremlin inside with dim red LED eyes? Give him a little screw driver or something.. Some scarry halloween prop..
(feel free to take any idea and make it your own.. I don't have the money or the time to do stuff like this right now.)
A64 3800+ Dual Core/GF8800GT-512/2gig DDR/10,000 RPM Raptor SATA 36gig HDD, 250gig 1394b/28" LCD