Great stuff there! As a few people have said before, it would be great to be able to rate maps et perhaps that it would be possible to display the levelshot within the pk3, as well as the complete name and other useful things.
To those complaining about security with the FTP, I have to say, there is NOTHING on the website that says "We will not use any data submitted on this website for any malicious purposes", which allows the TremCentral administrators and anyone who have any access to any information to use this information in whatever way they want.
Also, from a legal perspective, all the things said outside the Terms of Services (ToS) and the inexistent Privacy Policy (PP), whether it is on TremCentral, here on any other website is not legally bindable. This means that you can say anything on your website and have no PP, which means that by law, the owners can do anything with the information provided.
So, to all the administrators of TremCentral, you will have to create proper Terms of Services et a proper Privacy Policy, for your own security. If anything happens, then it is possible to sue you, which might be somewhat inconvenient. For your ToS and PP, I recommend you to read some good examples
(Adobe ToS, Adobe PP, Microsoft Tos, Microsoft PP), and then write your own. If you're too lazy, copy Adobe's/Microsoft's ToS and PP and then adapt it to your website, removing irrelevant information, and adding any information required. (and READ through those four examples, so that you get an idea of what a legal document sounds like, and what is necessary)
btw, I do realise that Terms of Services and Privacy Policies are extremely boring, and they go forever, repeating stuff over and over, but put it in perspective, you spent hours and money in creating this website and making it available to all, this could all be thrown out the window if you don't make a good ToS and PP.
Otherwise, great idea, just need to have a legal protection now.