@Corinnguard
Going through dragons by group, in no particular order
Gold: I've never liked the fish wings, so I've always had
some kind of problem with them. I can't find it now, but there's a picture out there that I absolutely love, which is (for me) the perfect fusion of Eastern and Western dragon traits for Gold. The face has the stylistic elements of an Eastern dragon, but the more wolf-like Western skull shape; it's long and somewhat sinuous, without looking full-on "noodle", and it's got clear muscles and such without looking chonky. All I can remember of it is that there's some kind of Asian-styled ship rigging in the background and that the primary colors of the image are red and (obviously) gold.
Silver: Believe it or not, the original 5e art is pretty good! I think the back legs/lower toros on that piece are too small (or the artist applied
way too much foreshortening), but everything from like midriff up is pretty much spot on.
Copper: Again, not keen on the fin-wings. The MtG art card for the Ancient Copper is decent despite the fin-wings.
Bronze/Brass: Personally, I've never been a fan of dragons based on alloys, with the
possible exception of Steel. So...I don't really have much opinion on these ones. I'd have done Iron and Cobalt myself (since the latter
was known during the Renaissance, albeit not by that name), since we can pretend that Cobalt, rather than being silvery like 90% of metals, instead has a blue tinge.
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Red: There's a version from 5e art which takes heavy inspiration from Maleficent's dragon form, and I appreciate that, even if Maleficent is clearly black-scaled rather than red. I certainly think at least
one of the chromatics should have that knife-thin face and overall body shape, but Red may or may not be the best choice. Barring that, the 4e look is almost perfect, just add back in the classic horns. Red dragons, like Golds, should look both physically powerful and magically powerful, and the classic red design does that. The new one (like too many of the new designs) looks
brutish.
Black: As noted, I think black dragons should look like Maleficent from
Sleeping Beauty. Jason L. Engle--a prolific D&D artist who did several pieces I liked in 4e--did a very good black dragon again for the MtG art. I can't
stand the new version, it makes my skin crawl and not in a "ooh, creepy!" kind of way, but in a visceral, burn-it-with-fire-right-this-second, unthinking-revulsion kind of way.
Blue: Honestly don't know how I feel about the fundamental design from
any edition. It's really busy, and the face is hard to parse. Either the MtG art, or the 4th edition version are my preference though, if I had to pick one.
Green: Arguably the most
classic of all the D&D dragons, so I think there's power in keeping this pretty "safe" simply because that kind of design should be included somewhere, even if it isn't universal. That said, this is one of the few "new dragon" designs I can see the appeal of; I'd probably aim for something that blends the classic look e.g. the 4e version with the updated look. Keep the face a bit more similar to the old, and
tone down but not remove the more dramatic frills and spines and stuff. The leaf-shaped wings on the new look are a nice touch.
White: 4e probably takes it here...but it's a tepid preference, sorta like Blue above. I guess I just don't feel they've captured a truly iconic appearance for white dragons yet.
I've never really had any strong opinions about gem dragons so I can't really say much on that front, other than disliking the (new?) reversed wings of the topaz. Every explanation attempted thus far in this thread makes me like it
less, not more, so...yeah.