Tracing is a very good way to learn the basics and build yourself a solid foundation, which you seem to have. 
To improve beyond where you are now, though, I'd suggest picking up some anatomy books - Burne Hogarth's series (Dynamic Figure Drawing, Drawing Dynamic Hands, etc) is my personal favorite. Looking at your pieces, I think this would be the place to start. You've got a pretty good grip on things, but there is room for improvement, and this stuff will help a ton. (Also, don't be afraid to use reference photos for poses. Those are extremely helpful, and not at all a "bad" thing to use.) My art had stalled out for a while before I picked up those books and started using photos for a helping hand more often.
Learning the basics of color theory is also a very good idea. It'll give you some ideas on how to design costumes, as well as how to light and shade characters once you start moving in that direction. Remember, black and white are tones, not colors. A plain white light source with plain black shadows makes the baby Statesman cry when it could be a more visually dynamic color that compliments the rest of the image.
What are you coloring with, out of curiousity?
In those images I used pencil crayon for some, felt tip pens for others. I think there is one that I watercolored as well. I'll have a closer look and edit this post to add information for a more detailed response.
Ok, here's the extra information I promised. Blackthorn, Enigma and the Heroes of the Lostworlds images are all colored in pencil crayon. Stella (1), Spectrum, Sathe and Sinta are all colred in inks using felt tip pens (with Sathe having her hair colored in pencil crayon). Stella (2) is colred with watercolors.
I tend to stink with real media, so I was curious. I know that colorless blender markers are awesome for smoothing out colored pencils (they get rid of the graininess and blend the colors together nicely when you're shading), but that's about as far as my expertise there goes.
With some of my new art I was thinking of going with digital inks and colors. We'll have to see how well that goes. I'm entered in the Legacy Coloring Contest too! I'd like to see if I could do all my art digital, but it's been a pain trying to adjust to the itsy-bitsy teeny-weeny little graphics tablet I have.
Tablets take a ton of practice. We've had our for a couple of years now, and although I don't get to use it as often as Su_Lin does, I'm only just starting to get really comfortable drawing with it. Lots and lots of trial and error. It's really worth it in the end, though - less mess is nice. And we love the undo button, precious. Yes.
These may be some of my older works of art, but I could still benifit from any advice you could give me. My art hasn't moved much beyond this point so any help you could provide would be most useful.
Blackthorn Scan 1
Enigma Scan 1
Unnamed Miscellaneous Scan 1
Sinta (mislabelled as Sathe) Scan 1
Sathe Scan 1
Spectrum Scan 1
Stella/Rei Scan 1
Stella/Rei Scan 2
Heroes of the Lostworlds Scan 1
Ok, so any comments on technique, lines, inks, coloring? I excluded all my other scans as they were basically just designs traced over other artwork, but the ones I presented here were my own with all my own little mistakes and whatnot.