One thing that is oddly distracting is the fact that gen 9 mons have artwork instead of pixel art for their PC sprites, and they just don't fit in with the others. So, I propose that users should be able to submit fan made pixel art for any pokemon that doesn't have a normal PC sprite, so everything can look more uniform. I'd assume it would be a similar process to how submitting regular sprites for pokemon works, but I've never been an active user during that process so I wouldn't know.
Here's an example as to what one of these sprites could look like, for context.