Ok, here is my idea. You can't really tell what it is, besides a sphere, but it would be modeled after the sun. It would have a semi-transparent shell that would be able to glow from light from led's. The leds could be able to change color according to the heat in the case. If I remember right the motherboard doesn't have temp sensors, so you would have to buy a separate heat sensor for the case and have it powered by one of the sata power cables and the heat sensor would lead into some sort of like voltage changer that changes according to heat and then you could have it hooked up to the led's strung around the case. You could also put a color+temp chart on the case somewhere so you have some sort of guide. You could also make them to where they can be yellow to red to follow the sun idea a little more. Led's are fairly cheap to run power wise, so I don't think they would draw to much power from the rest of the computer. Also you could make a solar flare on the case that would be split in three sections and could have cpu/hdd/and vga heat. It could also double as a handle for the door on the front of the case to access the blu-ray drive.
The sun itself would measure about 14 inches in diameter (it could actually be shrunk a bit). A good Hard drive for it would be a energy efficient one like Western Digital's 1TB green series hard drive. It would be installed vertically in front of the motherboard. A Blu-Ray player (a burner could also double as a reader right?) would be a great match too. It would be placed above the motherboard. Ram would be 2, 2 GB sticks with heat spreaders. Also on the case if you can see my writing on the picture, you could have vents on the bottom back and top (the mobo can't handle case fans can it?). Alternatively you could disguise the vents as sunspots around the case. Also the legs could be modeled after solar flares too. If I remember right the mobo can handle a couple of USB ports. They could be located at the top of the case and have a lid over them that could spring open when you press on it. The cost of the HDD is about $100, the Blu-ray player is like $100 (if you do the burner it is like $150), the ram say about $75, if you include the mobo in the costs it would come out to about $500. You could of course change components to fit the build costs.
You could also change it a bit to where everything is the same except the blu-ray actually sits in a box at the bottom of the sun that would also act as a stand for it. You could then size the sun down to about 7" in diameter and put the mobo in the middle of it and put the HDD behind it. Everything else like the solar flare (would just be attached to the sun) and the vents would be the same.