I stalk skin/accent threads a lot so I will link you some shops as examples. I guess it really depends on if you want to make things that are already popular and sell well, or try to make something that caters to a different aesthetic.
For example, I see a LOT of "pretty" skins that are like, soft muted colors, silks and draped things, feathers/angelic, sparkly, jewelry, that sort of thing.
Ravenhearst is a good example of this aesthetic that is super popular. The most popular breeds tend to be wildclaw, spiral m, skydancer f, coatl m, and imps but more male imps. So if you make something like that you're guaranteed to have buyers.
But, if you want to try something new... I say go for it!
Autopilot is pretty famous for making body mods and like, weird stuff lol, and despite their skins seeming kinda weird or out there a lot of people really like them! If you have a distinct art style people will recognize you for that and you'll get a fanbase that likes that sort of thing.
I really like monster skins, body mods, skeletal or gross ones, and theres a few shops that everytime they pop into the skin accent forum I check to see if they have anything new. The ones I can think of off the top of my head are
Doc's workshop (for like edgy robotic plague aesthetic),
Thunderwyvern I just bought a emporer skin from but they have a lot of like medieval armor or clothing on ancients, and idk if this shop is open anymore but
Kamazu makes amazing body horror skins.
Some other popular aesthetics I can think of are vaporwave and drawing profession type clothes on ancients since they cant wear them normally.
Really, I think it just depends on what aesthetic you like and would want to draw, or what your favorite breeds are. I can never find skins or accents for mirrors other than plague themed ones unless it's a holiday skin, so I wish there was more of those, but idk if anyone likes mirrors enough to make it worth it. I also have only seen someone selling a tundra skin once. So maybe you could tap a new market. What kind of skins do you like to buy? What would you use on your own dragon?
