Insane Micro Build Ideas

Hey there! I'm a new guy here. I've built a few gaming rigs over the past few years but I am now aiming at something entirely different: the idea of buying micro PC parts to create a PC that can be run in everyday items (such as a hollowed out old book: see this for an example).

I am looking for ideas or links that can point me in the right direction to get started.

Ideally, this is something could sit on the shelf of my entertainment system and use the HDMI cable and an OS (like Ubuntu for instance) to play movies from either the HDD or a USB flash drive. If it is placed in something small enough I could make it appear as if it were just another household item on the shelf, completely concealing the goodies that power everything.

Hit me with your suggestions/thoughts.

Thanks, and peace.