Vote goes for vertical, too. And because artwork tends to vary in quality, I tend to do my own so that nothing comes out blurry. If it does, I have only me to blame.
I started using Photoshop only a few months ago and thought at the time that all templates were created equal. Not true.
While everyone here has done a tremendously wonderful job in helping thousands of people organize their collection and have given them avenues to make their own custom covers, shenske and wiggy have made my overall favorite templates. They are very clean and organized, and leave room for many options.
Though I don't have any SNES games, I already started making my own for future purchases because I can make covers for NTSC games all the while using the SFC logo, which I much prefer.