Ever wanted to download a theme or gamer picture pack from the marketplace but you couldnt really tell what it would look like on your console? Before the new XLE xbox.com/marketplace would show you previews. Now they dont! WOOHOO!

But i found a solution to that by searching some websites.

Here is a very good website for previews on all sorts of themes. I am not 100% sure they have everything but they got a good majority of them.
http://www.themexbox.com/index.php

For gamer pictures i would use this site
http://www.mygamercard.net/gpscout.php
Edit: This site is currently down for maintenence, ill re edit this post to let everyone know when its good to go.