If you want new fonts go to dafonts.com and download some. Then just go to my computer and go to C:\WINDOWS\Fonts. Drag and drop the font into the directory and it will work for your photoshop.
For cool and easy backgrounds go to
http://planetrenders.net/renders/. I just save the image I want and then resize it and paste it into the sig for a background.
The easiest way to get better at sig making is to just mess around with it and experiment and see what works. You can also download brushes. Deviantart has a lot of good ones.