Don't have really anything to add but (oh god here he goes again >.>) while your texturing, clothing, skin/facial drawing has improved alot, your hair drawing seems to be the same as a year ago. Sorry ._.
If I had to compare it to your own works I'd say look at the thumbnail of "The social butterfly" and the enlarged Vasquez and compare it (because the head in the thumbnail and the head in the enlarged are pretty much the same size, not considering your original file on your desktop). Of course Kardashians hair is light brown and Vasquezs' is black but still, I guess it's the "flow" and the highlight placement?
If you're referring to technique, it's pretty much the same. But this is a character study, focusing on costume design, where "Butterfly" was a large portrait and warranted such detail. Honestly, I don't see where going back and repainting the hair in fine detail would greatly improve or be worth the time for a concept drawing.
I applaud your constructive scrutiny, but this is the point in the process where focus on punitive details will have to give a little for the sake of meeting design/implementation deliverables. I'm not going to sell people anything inadequate, but I don't want to continuously hold the project up to perfect every scene/panel/pixel. Otherwise I don't think this will ever get done, and that would do you guys a disservice.
I actually didn't even notice an issue with the brightness until I saw it on a different machine. My art machine is very bright. I used to work on darker settings, but I'd always miss details and such. I think I may update this one soon.
Yeah! I've seen various elaborate gamma-adjustment schemes--like at Monolith on MXO for a while they decided all the artists had to use one of those things you stick on your screen that supposedly reads it and calibrates the gamma and all that--but I don't think any of them work better or easier than this. : )
Oh yeah, another thing to check is that your Photoshop gamma setting is at 2.2--that's where it will render an image with the same gamma as it will have in any other program, like web browsers and so forth.