Alex,
I haven't read each post but I'd say philosophically: Go For The Bold.

In an exhibit people are expecting to see art, not pictures. The little, tiny and intimate images may work quite well in that type of setting but in a bank bigger is better.

Looking at the the thumbnail I'd first consider using a whole sheet of 11X14 and leave 2-3 inches at the top and bottom and let the background bleed into the paper without a trace of crop line.

Window mount 1/4 inch on four sides using 16x20 mat board. Frame it in the cheapest 16x20 frame you can find.

Just my $.02