I don't know if anyone else has made this suggestion, but...
What if we could be able to buy hats for your pokemon? Like a hat that any pokemon could wear. Maybe an universal top hat that any pokemon could wear, or if that's too much, maybe pokemon specific cosmetics, like a bow for Clefable/Chansey or a top hat for Lanturn, maybe air pods for Exploud? How about held items as cosmetics? Like a little squirt gun for Squirtle or a loaf of bread for Golduck?
I understand that for this, you'd need to A LOT of new sprites, but try to think about it, please!
Cheers, Legiix.