We're looking for a very clean and simple site. You will be asked to do 2 pages.
The first page will be the homepage. This page will contain the login form and form to upload your mp3 file as well as select options such as allowing downloads and what to tweet with the message.
Below that, the homepage should break into 2 columns, listing the most recent uploaded tracks on the left (including title, user avatar, and some brief stats), the right side will house a search bar, 300x250 ad, and then a listing of the top mp3s on the site. The search bar can also be placed somewhere in the header area if that works for your design.
Inner page should be 2 columns the whole way through. It should have the mp3 player for the track, title, more detailed stats beneath (listens, date added, yadda yadda), some embed links, and a place for comments. Right column should have a box showing the user information (sort of like tweetvibe.com) does on the right, a 300x250 ad, and some listings to their other uploads (if any).
As for logo, it can be really simple (like twitpic.com's logo). We plan to get the mp3 player designed in-house, but if you'd like to take a crack at it, be our guests :)
As for styling, we'd like to keep it simple and clean. Big, friendly text boxes etc. Here are some sites for reference.