I was snooping. goto youtube.com and query
'lego computer tower'.
there is some there.
maybe some ideas you might want to use.
AND when its done, post it.
Many would like to see it.
The Legos should support the motherboard well; I'd be more concerned with supporting the video card (if you plan on using an add-on) and the drives.
You might have to run threaded rod through the Lego stack and attach the standoffs to that to get decent mounting for the board, though... or, perhaps, use a dual-wall with a stiffener in between the stacks.
I'm a fan of new designs-- everything up until recently has been built around the same rectangular box, and it's not only boring, but downright stifling.
Actually, I like to go boxless: my firewall is mounted on a piece of HDF, using standoffs to mount the motherboard, drive and PSU. I blow the unit down about once a quarter for dust-control.
Well, you were talking about using (I assume) 2x4 bricks to form the walls of the case, correct?
I am uncertain whether those bricks would adequately hold the standoffs, so I thought that you could run threaded rod (or long screws) through the wall of blocks to attach the standoffs to. This would give you more support.
Alternatively, you could build a wall with 2x4 bricks, then back that up with a thin board or sheet of metal, run the screws through the backer material and the wall of bricks. This would be the most secure way of doing it. So that the outside of your case retains its distinct character, you could build a facade with another wall of 2x4 bricks (or 1x4, for that matter, for thinness).
When building something innovative(unconventional) in terms of computers you can never be too cautious.
And people treating their computer carelessly is no excuse to do the same with your computer.
http://www.pcworld.com/article/82184/avoid_static_damage_to_your_pc.html