Shared files already shows file size and last modified date. I will keep your suggestion of tracking download counts in mind for future improvements.
As far as skins I think it is more important to have a good out of the box experience with lots of good looking skins to choose from and to use as a starting point for custom skins without having to go and download and install other files. To me this is more important than file size of the package. I am feeling like a few of our skins are not as nice as others and could be left out but I would like to replace them with better looking ones and I think it is key to have skins that illustrate different menu approaches especially as this is one of the hardest things to do in skin design so having a lot to choose from when deciding which skin to start with for customizing is helpful. I hope at some point to have a skin gallery where it is easy to browse and download skins but we don't have that today and it is a lot of work to setup and create screen shots of various sizes and maintain it over time. I'm hoping at some point a community member would help with that but I'm drinking from a fire hose already and can't do all of that myself.