I downloaded the PokerStars Beta client today and I love it! It features resizable tables and "themes" that change the look and feel of the game. I am currently using a theme called "Hyper Simple" with a custom background that I found on the net. Here is a screenshot at actual size:



You can download the pokerstars beta from here: http://www.pokerstars.com/poker/download/beta.html

And you can get that background by right-clicking and saving the image below:



While we are at it here are a few more good custom backgrounds: