Yes, it is a matter of taste. My taste (as it were) is a vertical orientation for my square images. I have the same border at the top and sides, and more at the bottom. Or, slightly more at the top, but a lot more at the bottom. You are working metric, if I read correctly. I (being American) work in inches. I usually print a 9x9 image on a 11x14 paper, leaving 1 inch at the sides and 1 to 2 inches at the top.
Originally Posted by Oscar Carlsson
If 12cm is too small and 16cm is too big, then the obvious is to try 14, or ...