Welcome to the board, seen your stuff on DA a few times myself what brought you to OM? Mostly it was that Fantastic 4 coloring you did that really caught my attention as well as that slick looking Transformer. I haven't seen too many mechs that could look good but not serve polished.
Yeah, I'm certainly getting the feel of a comic a style specially in the first one. The man you done in the first one sort of reminds me of that how Superman's human father looked.
Hmm, comments..
1st one
Agree, with Jats on with the way how you used soft blends with strong cuts gives a nice effect. Really showed on the man's sleeve looks cool, sort of really smooth like a velvet shirt if you intended it. 
Yeah, the lens would look a bit cooler if you showed a bit distilled/fragment as the view cuts in on the sides. But, I think it's fine with the style you picked if you did that might've just been too much.
I think what could've been better is how you do your noses. Mainly, I'm just getting the feel like they are snarling at us from their nostrils. Also it looks, sort of gummy in how much shading is around them shows they are springing from the nose. Suggest, you just cut down the shading up around the top of the nostrils and slightly smooth them inward to the nose. Just like you done on the man in the first one, which looks alot better to me.
The woman's face appears to be quite chipmunk to me. Mainly it's just how tight the face is in her jaw and how sharp her ears are. I'd say the ears look sort of Vulcan! Somehow, I think they should be just a tiny less off the tops and cut them back more into her face. *Shrug*
I like the bit of crosshatching you use. It's a good way to direct around your view, somehow I'm not certain if you really need that bit below him on the shirt and such. It helps get a good sense of where his shoulder is at.
I think this would've looked neat, if you went for something that you haven't typically done before something maybe with facet (loose-fat) brush strokes with strong cuts giving you a frosted look. Something along those lines would really appear as a Christmas card! Specially I think that first one would've been badass if you attempted it like that. It doesn't have to be major feat I'd say just give it a bit of whacks with that maybe more on the clothes and slightly to the face!
2nd one
I get the feel like that man is really wanting to possibly punch you. Just sort of the way his teeth are grinded and the look from it he seems like a Navy Capt.
Love the cuts in the tie, cool looking and not tasking.
The beard to me is too overdone, just too much shin in it. Typically, it should be darker/less shinny than the hair. I think the lightning is just too high there, unless he uses a shit load of hairspray on his beard lol.. I think maybe if you just added in some low cuts on the side and a bit of shimmer were the hair just brushes off his chin would look nicer. It just seems to burn my eyes, atm..
Some of the hair highlights shine in both females is a bit over done in the curls. Really, it's just on the top areas I find where the hair rolls over.. I think it's just out too far and it would actually be in slightly at the crown unless hair is actually rolled out. Either way it's way it's slightly a bit strong and it's a bit too straight in both cases on them.
Specially on the first one, in the female's lower curl on the left of her face, it's just too straight not taking in consideration to volume somehow. *Err* It's just too solid, it doesn't fade out or let go in some areas as it should I guess is what i'm trying to say..
(slim to none difference in highlight)
I find your hair approach in the first one on the man was more in suit to the style. The scratchy yet not over shined goes more into flow with the whole image itself. I believe if you just did that to the others more similar, it would've been alot nicer looking. 
Alright, hope too see some more imaginary stuff on the board. Looking to see your colorings next leaning more into characters/comics. I doubt my comments helped much..