I once had an exhibition were I actually sold more small prints (12x12cm) than bigger prints. The small photos were in 70x50cm mat and the bigger prints in a little smaller mats. The small prints were all a little darker (lithprints) and the matting (off white) but the contrast seemed to have worked because people wanted to know what the small dark square in the middle of the white was furthermore it looked a lot like a modern painting (Malewitsch). The bigger is better philosophy is not necessaraly new one only has to look at Rubens paintings they are huge, funnily enough the most powerful Rubens I've ever seen was no larger than 5x7in (a gallow in front of storm clouds and hills).