Basically it is a hiding the excess.
Your drives being IDE means there is not much you can do to hide the cables except jam then in empty bays, the psu molex leads could be rationalised to the barest minimum required and the rest tucked away neatly somewhere.
Do you really need the usb header? and the other one (ribbon cable, gameport??) that's a heap that would be easy to tidy up if you don't.
The 4 pin 12v lead that currently runs across your ram could probably be tucked behind the top of the m/board and brought out on the far side of the cpu cooler and run vertically down to the socket, same with the cpu cooler excess wiring, tuck it behind the m/board.
Can you do without some of the molex plugs in the lower hdd bay? less wiring means less to hide, also can you re route them as they would appear to be affecting the airflow from the front case fan.
EDIT: there is a lot of space down the sides of the psu and drive cage to hide wiring in