Those on the right are folder tiles - those folder icons are very probably having some effect on the tiles. Seems like a Windows kind of thing. (Or maybe it's because of Rihanna, on the left: she sees things rather big!)
Tiles are awesome in other ways too. For instance, I use them as an alternative index system for Word documents. It's a lot of work to set it up that way, but once I did it, it was just awesome. The magic of Directory Opus.
I also once requested for a different way to define the size of the entire tile (not one-definition-to-rule-them-all, but one which can be set up differently for different file locations). This request did not bear any fruit so far, but I'm still satisfied with the system in spite of certain limitations.