Here's a way you can get a designer look for your painted walls. With a roller, apply an oil paint glaze over an already dry base coat. For your glaze, mix two parts oil-based paint with six parts glazing liquid. Lift off the glaze with a rolled-up rag. You can repeat this process with different colors for a layered look.
For more on finishes, consider:
Radio: Faux Painting
10 Creative Uses for Chalkboard Paint
8 Ways to Age, Distress, and Add Shine to Your Next Project