As for the face, I actually like it. Very stylized and charming. I find the newer one much clearer in its expression. The blushing effect is a bit hard to make out, though. Not that you have to change it to some kind of eye-searing pink.
The character sprite's style seems familiar... Was it, by any chance inspired by the
Mario and Luigi RPG games? No, that was probably just the antialiasing.
Most of the problems I have regard the palette, which overall is very bland, that is to say, it's a straight ramp from light to dark or vice versa, in other words, monochromatic. (Yes, I've said that many times before.) It could use a bit of variety, for example, tinting the shadows to blue, or just picking out a less generic color, in this case classic cyan.
There are also quite a few jaggies you haven't gotten rid of yet. Take for example the large spike on top of the newer portrait's head. It's probably supposed to be a smooth surface, in which case sticking to a straight-on diagonal line would have been the better option. Yeah, it's hard to explain.
This link puts it better than I do, and has examples to help. Just scroll down until you come to jaggies. (Reading it entirely would also benefit your technical skills seeing as it's a tutorial, a good one at that.)
Seems you were going to smooth things out with a bit of antialiasing, but frankly, it didn't turn out very noticeable especially at this scale. Hopefully I retained the aesthetic you were going for. Might have gone a bit overboard with the AA'ing...
