I've been pondering this and came across a great, fun tool at:
(join up the line, if it gets split!)
You can try out mount sizes, colours and frames. You can even upload your own image, and find a combination that works.
I'll probably cut my own, rather than ordering from them (as I suspect I'll want quite a few), and I'll do some real tests first, but it's given me some good ideas as a starting point.