Thanks. If anyone's wondering, the reason for the odd resolution is because the wallpaper was made for Standard Definiton TVs(remember, Playstation 3 wallpaper).
If you mean to make an image link in your sig, just do it like you do any link, but put image code in place of where the text would be. Example:
[url=www.sitehere.com/][img=image url][/url]