Why didn't I think of this? Pick the size & fabric -- DIY Memory Foam Rug via the idea room, love this! Another note - memory foam rugs are beneficial to those of us who have brain injuries - no tripping and falling!
DIY: How to Make an Area Rug Using Carpet Samples - info on the types of carpet samples to use, how to lay out your design and the type of adhesive to use. This budget-friendly project would be great in a play room - A Scoop of Sherbert