Hey there Heroid,
I'm an artist too and trying to break into the world of comics after years of doing photo-realism and portraiture (Of people AND animals... what people will buy for their dogs is beyond me but whatever...

). I've always have a difficult time looking at other people's art without a critical eye so I hope you don't mind some constructive criticism.
I like some of the choices you have made with your art. I can tell that you have a decent sense of anatomy even though it varies from piece to piece. A couple of your pieces also show a good sense of foreshortening, which many amateur artists lack these days if you ask me. Expanding and doing more of it will always give your work a more professional feel.
Another thing that I think would improve your work greatly is playing with varied line width during the inking stage. I imagine you're using a single felt pen to do all of your inking or maybe a couple of different sizes. If you live near an art store check out brush pens (
these are my personal favorite). Also try inking hard shadows prior to colorizing shadows into a piece. Blocking in shadows with the pencil using simple line shading even prior to inking helps you plan out how the inked piece will look. Use finer pens for finer details and thicker pens for more broad details. It takes practice but your work will become much better when you learn to apply solid line economy during the inking phase. Don't be afraid to buy some nibs and some well ink, adding that to your inking arsenal gives you even more command over how lines will look before you reach the color stage.
Colorizing a piece in Photoshop or Illustrator is of course the last step in the process and, though your use of color is pretty good you could stand to experiment more in this area too. Hard shadows should almost always be inked in to accentuate certain aspects of a piece but that doesn't mean you should ignore soft shadows in the colorizing stage. Also don't be afraid of highlights either, they can spiff up a piece rather nicely if used correctly. You can even help your coloring out by blocking in the highlights during the pencil and ink stages, simple outlines with a fine tip felt-pen (.20mm Micron) is what I generally use. Be sure to master a bit of color theory too as this can help ENORMOUSLY in the long run. You can find some good starter information on
Wikipedia but use that as a jump-off point.
Out of all of this advice I'd argue the best bit of information I can give you is to be afraid of getting stuck in a rut. Always try new things and expand your horizons. If something works, great! Keep it! But don't play with it for too long!
While asking non-artist friends if they like your work is great, ultimately it's just an ego boost (Which all artists like

). Seek out the most professional artists you can talk to and always get second opinions your work and your clients will thank you with more profit on your end

.
Best of luck!