We love finding projects that have a big impact but don't take much time (and we're definitely sold if the clean up is minimal). These simple stripes on a pull down shade add some graphic interest to a cheap version from Home Depot and it's much easier than you'd think:
We found this project on How About Orange and loved the idea of 2 simple stripes on the bottom of a shade and imagined it would be a pretty simple project involving some paint and some tape, but in reading on we found that it's even simpler than that. All it is is colored artist tape which doesn't leave marks. It can be removed easily from the shade when you're tired of it and you can even swap the colors out.
You could also apply the same idea to a wall or a border near the ceiling. No messy paint and no clean up. And if you don't like it, it just peels off.