At some point, it's less, also, about the size as much as it is the quality of the picture. This reminds me of OkCupid (the dating site). They did an analysis of the quality of picture (and camera used) to measure their effects on click rates and messages. See http://blog.okcupid.com/index.php/dont-be-ugly-by-accident/

Looking at how some really great sites are doing, too, there are sites with massive pictures, but if they're not high quality, turns out to look like a cheap site.