There is a website based design tool called "Olioboard". This is a site that allows you to visualize various design elements in a "mock-room" before you buy. They have images of products from numerous retailers that you can plug-in to a "room" of your choosing.
Below is a sample listing of some of the vendors featured on Olioboard:
One Kings Lane
The Land of Nod
Right now "West Elm" is sponsoring the "Pattern Palette Design Contest". The challenge is to incorporate items from West Elm's pattern palettes in a living room setting. The photo above is an "Olioboard" that I created for this competition. You can check out and/or vote for my entry by clicking here.
To check out all of the details on the "West Elm Pattern Palette Design Contest" and/or create your own entry click here.