Here's an inexpensive and creative way to decorate a floor. Roll on a coat of deck enamel (the color of your choice) and allow it to dry for a couple of days. Then choose three contrasting colors to splatter on top. Fill your brush liberally and move it from side to side, tapping it with a stick. Splatter all three colors at once, so you don't have to wait for each one to dry. When it's thoroughly dry, apply three coats of polyurethane to protect the finish.
For more on painting, consider:
How To: Paint a Wood Floor
9 Incredible Faux Finishes You Can Do Yourself
8 Ways to Age, Distress, Gild, and Add Shine to Your Next Project