Okay, I haven't done this yet, but Holly at Decor8 posted this the other day and I'm going to try it. Take a fake grass mat, draw your design on the back, cut it out and ta-dah! New cool mat! Holly links to a Danish site with a downloadable pdf pattern but I'm going to try to freehand something and see how it comes out.
Holly's got some crazy Danish connections so she always has something new on her site. I love so many foreign language blogs but I'm obviously only there for the pretty pictures--thank goodness someone out there takes pity on me and my failing language skills!