guess you'r new to this? well not bad for a first few sigs, but here are some general tips for you: - work on smaller canvas, 400 - 130 is more than enough for your avarage sig - work on your text or just leave it out, text isn't always necisarry - (this may sound lame but it's true) look at the tutorial section, there's a lot of great stuff in there on sigs and general design tips
Try smaller sizes like dinges said, and yeah, try finding some tutorials though, they will really help you out a lot. You learn so many new ways to make effects, backgrounds, etc.