If your referring to the big purple thing, someone on here did it for me, and then I just played with the colours a little and added my name... Unfortunately I cant remember who it was So apologies for that! I'm sure someone will be along soon with the answer, this place is like that. Lovely looking interior too!
I did one for Daisy Jukes. There is a thread somewhere with a few designs on there - you save the pic of your choice to your computer, alter it to your needs / taste and then save it on a hosting site (photo bucket or similar) and then in your account settings there is a signature option where you can paste the img link.