Secret: A metric ton of zip ties, zip tie mounts, and time.
Wire only stays so neat when it has a place to be, and zip ties are perfect for that. Bundle wire going to the same place (for example, PWMs from the DS to the motor controllers or power wires from the PDB to motor controllers) in a neat fashion, meaning line each wire with the same color facing each direction, and zip tie the wires together every few inches.
Keep everything standard. Use the same zip tie colors, crimp connectors, and wire. It looks better.
Actually, thinking about it, thats really it. Just set out to wire well and you will wire well. If it looks pretty, you are good.
I actually don't have any pictures on hand of the wiring on our robot, but
this was us a few nights before bag date last year.