Not entirely sure, I usually just drop the PNG into unity and resize it from there. A few different rectangles and squares would probably be fine? I'll look into the 9 slice a bit later. The one on the top of the page there is pretty good... maybe one that is a little bigger or fatter. Some pre-constructed buttons? The rest of your stuff is really useful, I'll put your name in the credits.
I was looking at stuff like this thinking you had some pre-sets in PSD or something. Anyway, my fault.