Your art looks very nice. But it's hard to see how well you detail them when they
are shown so small..
If they look that good full size, and in traditional art they would be worth a nice
price. At least $50 dollars. Of course you may have to do commisions to get
that and more. Check artists websites. They often tell what they charge.
If your worried about people stealing your work. Post them with the word sample
or some other word or pattern in a transparent overlay..