The 50MB download cap, which is huge considering most files are less than 1MB, is to allow you to sample what WinCustomize has to offer and to help you decide if you'd like to be a subscribing member. A subscription here is just shy of $20 for two years, less than a buck a month and you'll have unlimited downloads. It's quite a bargain
There are other skin archives available on the internet, but I don't believe you'll find one that has the expanse or variety that this one here has.
Also, because of it's association with Stardock, which creates most of the programs that WinCustomize hosts skins for, you can skip the subscription and get unlimited downloads by purchasing just one Stardock program. The full version programs, like WindowBlinds, have additional features not found on the freeware trial versions.
Either way, like CerebroJD said, you'll be helping to offset the bandwidth costs for this site
