Hypothetical Build

So lately I have been thinking of doing a purple, white, black themed-build. Here's the part list

http://ca.pcpartpicker.com/p/XFK4hM

I would change the power led to a purple one like in this build (and try to change the ones on the stock fans too in order to have more fan), and I would call my build Nep-Nep (I'm serious)

Would it look better with purple braided cable instead of white ones? With white-painted GPU? Any possibility to lower the price? Am I crazy?

The build idea sounds absolutely amazing. The purple braiding would go good with a white GPU in my opinion. Perhaps a custom cable set that includes a purple to gray to white 24 Pin cable and solid purple for 6 pin/8 pin.
Also if not too crazy of an idea, get Nep-Nep herself or something ralated to Nep-Nep, lazer ingraved into the acryllic and possible some strong purple LEDs to illuminate it. Yeah I know sounds expensive.

I don't know what would look better, but you are definitely crazy. Luky for you so is practically everyone else on the internet so you fit right in.
Joking aside, painting the PSU is not something I would do. The white cables would really jump out but if only the fans are purple I don't think the colours will be well balanced. Maybe drop the black and go white and purple only? But then you'll have to paint the PSU or buy another one... Its up to you I guess.

I have thought about it too, like put a figure inside it but it's kinda expensive ^^ and for the laser engraving I would have to find somewhere that have a laser engraving machine but that would be cool...

What I would do it's to have purple led strips illuminate the white components so it looks more purple-ish (at default to have purple components) in order to have more a purple/black build with some white accents. And I wouldn't paint the PSU, but the GPU, but it would be after deciding which look better (between black and white).

Aha, I read it wrong. Painting the GPU would look badass indeed.
The LEDs are a good idea. This build is probably going to look very nice.