Art and artists: How are they important to the game and world?
Art style: How does it make a difference?
Character depictions: Are inclusive and “cool” mutually exclusive?
The D&D logo: What does it mean to you?
Those are some solid questions.
First, art is vitally important I believe to any imagination game as it inspires the reader who can then turn around and use it for play. The players are going to be imagining their character and all of the other elements of the environment. Artwork supports this by increasing player communication and connection beyond the spoken word. Artists shoulder both illustrative duties (for answering questions such as "what's a mace look like?") and inspirational ones ("That's what walking up to the Temple of Elemental Evil looks like? Kick ass!")
As you are an artist I find it difficult to imagine you do not know why style matters. As an old schooler I can only suggest resisting the urge to brand a style upon D&D. It's smorgasbord kitchen sink for a reason, inclusivity breeds strange brews. Have cartoons, have awesome full page dragon oil paintings, have sketches, go multimedia even. I like magical realism my self, but let's not limit an edition focused on bringing everyone together. Each piece should be internally coherent I believe, but that's up to the team as well.
No, inclusive and cool are not mutually exclusive. Even if you're using both to define a single depicted character, it is possible. But don't let those be the only two to drive every singular creation either. I can imagine persons visually identifiable both inclusive and cool. But don't finding such for yourself stop you from portraying exclusive individuals or the obviously uncool.
D&D Logo... ... okay, that's a boatload of difficulty there. This is a "final" edition, no? And a logo really is at the heart of branding IMO, so it's going to define part of every element published for the game. This is tough. Look at other work for inspiration I guess. I like googling the LotR logo. I'd prefer classy, but, y'know, this stuff changes over time too. I'm sure some folks here remember the wizard TSR logo - or the lizardman perhaps?
Also, great first pic: