This might be a 'lame' idea, but I saw a computer on a commercial for an antivirus software that had parasites, worms, bugs, etc... crawling out of and all over it. I duno, that's kind of a hard thing to think up; a funny/scary computer costume.
My friends told me to go as the Red Stripe Guy from the beer commericials. Get that tail tuxedo and get a bottle of Red Stripe...all because I can mimic his lines pretty well from commercials..."You are very Ugg LEE" Ao funny.
Kinda late to that party on this thread. But I saw a fun idea. It was a guy with basically a box over his head and a sign that said "kissing booth".
But it was designed to look like a booth. Pretty funny.
When I was in elementary school, I made my own costume ... I was an Apple II computer sitting on a table ... all out of cardboard. My face was a little cutout in the computer monitor. Unfortunately, I was way too advanced for my time, and all of the other little kiddies thought I was a television. I remember being very very upset because I worked very hard creating the costume for weeks and I didn't understand why no one could figure out what I was.