I'm partial to beige generic computer cases myself.
Make sure it has a Compaq sticker on it!
It's already really cool surprisingly, I think because the case is so open. The PSU breathes through the bottom, so I don't think I actually need any additional ventilation at this point.
It would benefit from a couple intake fans and another exhaust fan at the back; especially since your GPU vents back into the case. I have a completely open case with the CPU and GPU on their own aio radiators and I still have to put a desk fan to blow over the other components or I will start to notice micro stutters in very intense games.