I really like the colors and how you've them in the first set of portraits. The only thing I thought was a bit strange is the light sources. The high-res face seems to be lit from the lower right, while the hair and body is lit from the top right corner. In the low res version the guy is lit from the top right corner, but the fire background would to me suggest being lit primarily from below or the side. Lastly I think the large amounts of pure black in the hair should be swapped for some less sharp color.
Just my 2 cents, I really like the style though.