Is that a cat's liver ( can't tell from the pics)?????
Looks like hair to me.
With that 92mm Tornado fan running on 'high' all the time, I'd say you're "collecting" dust on your heatsink from about 7140 cubic feet of air every hour (119 cubic feet per min X 60 mins) not counting how much air is being exchanged throughout the case by your other five fans. Multiply that by how many hours you leave the computer running every day and how many months you have had the computer running like that and you can figure out how fast the dust will build up. The fact that it's also sitting on the floor may also be another factor in the dust collected since dust normally settles and may get picked up by the fans near the bottom front of your case.
I usually blow the dust out of my case every three to four months. My laptop seems to need a bit of "canned air" through the vents every month as; I run it on the floor sometimes and the fact that the little Delta fan is on the bottom picking up carpet fibers and dust from the floor is probably one of the reasons why the it builds up dust quickly. One good blast will send a clump the size of a dime out the rear vents. You can look into the fan intake to see what I mean.
I was just talking to your next door neighbor the other day about his computer. There's a problem with the onboard video we're trying to fix; I figured out the connector must be bad but he's getting a separate video card put in. You should have seen the inside of his E-machine the time we opened it up.
Your "cable management" does need work although I've seen worst. Bundle them up as good as you can and tuck them either in an empty drive bay, to the right of your drives, or behind the power supply. Raising the case about 18 inches off the carpet will also help.