The PiS1

For assembling, just screw the bottom to the top and glue some parts if you won't make them functional (recommended).

You can make some functional buttons as you want, but I left it as your choice. The dvd cover is prepared to be hinged. There's no need to print the feet if you're gonna make them with rubber. The power led can be functional too, it can be made with the mold (the rectangular cube with a hole on the top).

It's correctly scaled to fit a Raspberry Pi. Let me know if there's any problem with the size, I made it based on the scale of a famous STL model of a Raspberry Pi case.