I'm not one for making my desktop case a technological sight to behold. Whilst I can appreciate the aesthetic of black or grey boxes with colourful LEDs lighting up fans and the internals, I'm far more interested in seeing desktops as pieces of attractive furniture. As an example, of two of the rigs that I've built, one was inside a mahogany topped desk and the other (my current) inside a Victorian carpenters toolbox (no pics as I'm too new to attach them).

So far, I've found the biggest challenges to be providing enough airflow for cooling, and soundproofing the fans enough.

I'd be interested in what other non-standard cases people have used when building their rigs - I saw one once built into the dash of an old VW beetle dashboard for instance.

Cheers