I don't think a non-rectangular edge is bad, it's just the one you have there is so random and erratic. Looks like you made a shape with scissors. The rest of it I quite like.
And I think it all depends. Cabulb's sigs are so wild and packed that a uniquely shaped border would send it over the top. ^^ For me, I experiment mostly, and try not to fall into a cycle of using the same exact style for everything I make. Although I always give it depth, using transparency.
Okay guys, come on. This is a nice topic for friendly exchange and discussion of art, not a boxing ring. Regardless of who's right or wrong, this is ridiculous. Enough.
I'm going to ask a moderator to clean this up and put a stop to this nonsense if it keeps on...
It all looks really fuzzy, and the picture of Davey is really small and low quality. Try scouting around for a better picture of him, and experiment with a different font and effect.
I don't mind the red, I actually like that dark color scheme. Just toy around with effects and the font. Adding glow is a notoriously overused effect.:PPlay around a bit!
Outer and inner glows can be pretty (eg. most of my signatures actually have an insane amount of glows). But subtlety is the key, that's why they don't rape your eyes (anymore).
On a small resolution, anything larger than 10 px is overkill. Also, don't push the opacity past the 85% mark. Depending on specific compositions, range and contrast, 65% to 75% (default) is often more than enough.
To alter the range of colours/theme of an image, use gradient overlays (ask me if you want to know more about them).