The skins that I ordered from Decal Girl arrived earlier this week. Each one has on it a link to a download for a background that exactly matches the “hole” in the screen border. This means you can get effects like the one above. I really like this, although if I use the same background for my desktop it makes things confusing, as I try to drag things into side of the device.
If you want to make your devices nicely unique and protect their surface a little (note the play on words there) then I reckon they are well worth a look. The picture, since you asked, is of a rock pool at the seaside on the Isle of Man. I liked the shape of the cracks and the blue sky above.