Hmm, your sprites are good for someone just getting back (and much better than anything I can do).
I'm just concerned about the outlines of some of them--they just appear rough at times. I don't really know how to describe it. Just take Aquana's or Blaid's heads for example. They feel a little sharp, and while that may be exactly how they're designed, the dark outline accentuates it too much. Also, the shading is mostly really good, but it could use some dithering in places; namely on Pyne's grass and Aquana.
Blaid's overall appearance is choppy in my opinion, and it looks like your least worked-on sprite. The brighter green contrasts too much with the rest of the sprite. You could either use a slightly darker color or apply a little dithering between colors.
That's all I've got for you, I tried to be more helpful than just saying "Great sprites man!"