For me diversity seems to mean applying modern racial, sexual, physical demographics into all fantasy settings that should be depicting the fantasy world, not our own.
Other than the obvious (existence of magic, non-human races etc,) how do you believe that the fantasy depiction of demographics designed to appeal to the broadest modern audience for the game should differ from those of modern demographics?
But what body types should D&D or other games depict? Glasses were mentioned, but what for creatures with no eyes? Should you have wheelchairs for creatures that never had legs?
Why would a creature with no eyes have a need for glasses? I could definitely see a creature with no legs that has trouble moving around on land using a wheelchair or similar aid to get around however.
In terms of the body types for humanoid adventurers that D&D and similar games should depict, I would like to see a range. For example I'm not a fan of a lot of the stylised bodybuilder look for warriors by Frazetta et al. I'm willing to tolerate a few examples of it for the sake of diversity however.
Overall, I'd like to see a range of body types for humanoids, even within each lineage.
Hiw about skinny and fat for amorphous creatures? All of these are, I think, plasmoids? Those slime or ooze like monsters. If it was a PC race, hiw would you depict those body types? Would it make sense to depict them like hunans?
I mean, amorphous creatures are literally defined by not having a fixed shape. Working out what skinny or fat in their context would be practically impossible.
For me, and good question, thanks for asking; it is and should only be about art of humans, not any of the monster of fantasy races. But, we do not need art for humans at all. We already know what humans look like.
The Monster Manual's art is there to show what the creatures look like. I think most of the Player's Handbook art outside of the Lineages section isn't.
I believe the purpose of most of the PHB's illustrations is to spark the imagination: to evoke the fantastical worlds of D&D, to provide aspirational examples of the adventurers that players could play, and to depict some of the situations that those adventurers will be in.
This is why I think that they're likely to make the PHB art as representational to the broadest demographics of players as possible. Some players want to see themselves in their characters. Others will play characters wildly different. Outside of potentially harmful depictions (such as the "chainmail bikini" situation) and within the bounds of the art styles of their current artists, I think we can expect to see some quite diverse pictures.