Base-board is screwed to a CD-ROM with some 4mm irrigation pipe 'stand-off's. It's then sitting inside the upper-half of a 3.5" FDD case.
The fan is just sitting on the hole from the FDD motor/flywheel (the picture is with it turned on). It's powered from the 5v supply in a rather unreliable manner ...
It does the job anyway and seems to keep the chips quite cool. It's a 12v fan running off 5v so it's essentially silent too.
The camera really shows up the (emabarrsing level of) dust, as it's usually too dark for it to be quite so visible. Particularly as it's under one monitor/next to a laptop so my eyes are normally blinded by that.