Ok hmm well I was bored for one and I noticed this was the forum with the least amount of signatures I've ever been to... so I'm starting a trend! (or at least trying to)
Show off your signaturial skills!
My latest weakly attemps (haven't done any in a while so...they ain't great)
I'd say: readability. Why not use a black background for the site, with small dark grey fonts ?
Well in your case Borgleader the signature is usefull, if that was not I would consider it as a nuisance I'm totally open on the artistic side, but imo as far as forums are concerned the thinner the better.