^^^ What Archmage said.
Plus I see some pretty pictures at the beginning of the thread. Whoever made those should make some more!
In theory it is (or it will be) possible to write i.e. a Phyton script (Mr. SID come on!) to convert any image into pixels using i.e. Hein or Carrion's pixelling style.
So I could create my original artwork in PhotoShop and then convert to C64 in a best possible way (preserving hand pixelling quality), it's even possible to breed a few styles (using genetic algorithms) to create hybrids (i.e. Mermaid/Archmage).
Sounds too scary? ;-)