Yea, the layouts work just fine. However, the only site I've ever changed is party. Most every poker site just uses some type of image file to display the tables. They can easily be changed/swapped out. As for 4 color decks I suppose you could simply modify the files yourself and substitue in different colors. As long as the filenames remain the same it shouldn't be a problem. However, if you screw something up and change filenames / cards it might display the incorrect card causing catastrophic losses.
Here's my setup for party if it gives you any ideas...
2x19" monitors custom party background - click to enlarge
http://www.pokermods.com/mods/
Pokermod 'Easy Eyes Black'
I also went in and deleted that annoying sidebet button, that thing just wouldn't die I think they finally included an option to hide it or maybet that is the blackjack icon...
-Moose