The original inspiration came from Domino's spread on Mary McDonald's guesthouse where she painted a large sisal rug. While the scale and bold color contrast were interesting, they were a bit over the top for my personal tastes. Still the idea of having a geometric pattern enliven a dingy rug was intriguing...
After scouring the web, I've found two fairly clear set of instructions on how to go about beautifying (destroying?) your carpet/rug. The consensus seems to be that coarser, sturdier products such as sisal, jute, seagrass and berber are more receptive to paint than your standard plush carpet, which would become impossibly hard and matted if treated with paint.
How To Instructions:
Click here for Curbly's DIY Maven's easy to follow instructions.
The instructions above are intended for creating a border, but I think the same principles could be applied in order to create a patterned design.
Pattern Inspiration Ideas:
Trina Turk's Trellis and Sunglass Prints for Schumacher
Kelly Wearslter's Asian Trellis Latticework for Schumacher
For barefoot comfort and for aesthetic reasons, painting a limited area, like a border or a pattern, rather than the entire carpet or rug seems like the way to go. Paint obviously changes the texture, making the carpet hard and crunchy if applied too thickly. I think that if we do pull the trigger on this one, a simple tone on tone pattern will work best.