Or perhaps make a few themes for a program. For example Panucci has a pleasantly barebones look at the moment, (which I personally prefer), and has only two different screens, so might be a good showcase for a range of experimentation.

I have nothing to do with Panucci except it's virtually perfect for my listening uses, so I don't even know if it will support themes, but it's worth a shot to contact thp on this forum, and have a chance to show your chops in what may turn out to be a widely used app.

Joe