I was chatting today with a youthworker who used to design magazine layouts professionally and we were talking about the various things we use for backgrounds.
I've used typogenerator which works very simply and transforms text into a funky background. You sometimes have to wade through some dull ones until you get a good one as it is randomised.
Also I've loved the discovery of this website with fonts from films and bands. A really funky font can really transform a dull poster into something rather special.
You can make ordinary photos look pretty funky with magnigraph. It even works on our dog who is black and white already!!
The other trick I use is painting something and then using it for a background. I guess this is kinda more labour intensive but it's pretty effective!
Today Jo had a link to this thing called wordle which creates lovely word clouds from text or websites. I've seen this kind of thing before but I rather like wordle. Here is a wordle of youthblog - had to include this because of the prominence of creosote - just for you youthblog me old chum!