Ok, first off, I have no Cherry keyboards (yet), my collection being exclusively 'vintage' Model M's. So I don't really go in for blinging up a keyboard. That said, fuus, your keycaps don't look especially well-done. You called for constructive criticism, so here it is -- improve your technique. I can see the edge of the color spilling over onto sides of the keycap that you did not intend on painting, which is distracting and well, ugly. Now, jeroplane's keycaps are an example of keycaps I consider eye-stabbingly ugly but are clearly the product of great skill. Jeroplane's keycaps look smooth, the paint looks evenly applied and no brushstrokes can be seen. Again, they don't fit my sense of style, but they are clearly well made.
For all I know this is fuus' first attempt and he'll get better.
As for whether fuus should be allowed to sell his keycaps in the Classifieds, he should be. Caveat emptor, baby. If fuus provides accurate photos of his keycaps, then leave it up to the forces of the market. If the GH admins want to do something to allow people to rate each other as sellers using the forum software itself, that might prevent people from being ripped off, or selling crappy goods. There should be no rule forbidding people from selling crappy products -- some might consider keyboards I value to be 'crappy' and thus deprive me of a potential purchase. A 'crappy' product is acceptable so long as it is not fraudulently presented. Give me big, high-res photos so that the 'crappiness' comes through in high fidelity.
Now that the constructive criticism is over -- I think handpainted caps are fugly in the extreme. But if you love them, have at it. Even fat people should be allowed to have sex, right? I should not be forced to watch, but they shouldn't have to hide their rolling, gelatinous masses, either.
