Here's a pic with the light switch included:
If you'll notice, this is as wide as this piece of wall gets. There is molding to both sides and on the left is the boys' closet. The mouse hole fits perfectly here. It's a small, but fun detail.
And here's a close up of the mouse hole:
The color is a bit faded thanks to the camera flash, it's a bit darker in real life. And yes, for the record, mice have a real problem making their mouse holes stand up straight and not lean to the right.
*****
Edited: because I forgot to mention the supplies used. These are just basic acrylic craft paints. I also used a black sharpie to clean up the lines a little bit.