A couple of evenings later I had the layout figured out. The mobo tray and HDD cage aren't attached yet because they will be getting a matte black finish in a few days. I predrilled some holes for pop rivets though.
The paintjob was a bit of a failure for me at least but then again this is the first time I've ever done it. I've read the basic instructions for PC case paintjobs which all include sanding, doing a base paint, then the actual color paint with sanding between coats etc. First of all, I didn't sand or do any kind of base coat (noob behavior, I know). Instead I did many coats of matte black using Maston 121 paint. After several layers I did a clear coat with some basic Maston spray (can't remember the number). Also, due to a massive failure I pulled off one day I ended up using an automotive chassis protection paint on the cover. It was purely experimental but I think it made the paintjob more durable.
Far from perfect but not too bad for my standards :)