I've got a few old Raspberry Pis knocking about, and I was challenged to make a case that looks like my old Dragon 32 home computer. This is what I came up with - and (with a bit of overclocking) it runs a Dragon 32 emulator on RetroPie fairly well.

It's 1:4 size, with the lid best printed on its side using tree supports (as per the pic from Cura).

Note: to be able to fit the Raspberry Pi 1B in, you'll have to desolder the GPIO headers.