TheMoreTheMurrier's Profile

You have us nothing to go on in terms of the look you want to achieve. So...we're left throwing darts in the dark. I think an overlay of wood with a lip on the front is an excellent idea. Paint that whatever color you want, or wrap it in a decorative paper (e.g. wrapping paper) that you can change on a whim. Consider something thin...like the thickness of a pegboard...heck, that might even be a look you would consider.

If you want this to hold weight, and if you have pets or kids or drunken visitors, consider a strip of peel-and-stick velcro. Put one side parallel to the window at the back of the sill and the second piece on the wood you are installing over it. That way, it'll stay put.