I'm going to scope out some patterns and try to come with some ideas of how to incorporate the lighting. Hopefully something will pan out.
Honestly, if I drop the cash on a 4 port power supply like this one:
http://www.thatscoolwire.com/store/item ... SEQ-4-6VDC
I'm guessing 2.2mm cord would be best, as it still puts out enough light, and it would be easier to control with multiple colors compared to the bigger 5mm.
after that, the cord itself is only about $1 a foot, so customizing it for different designs wouldn't be terribly expensive after the initial investment. Plus, I'd imagine I could light 2 different pumpkins with the 4 strands.