Battle animations with no reference (eg. Not simply replacing a Mauthe Dog with Umbreon) take many hours to create, in case you aren’t aware.
Overworld sprites are easier. I did the first 151 here:
https://feuniverse.us/t/ultimate-graphics-repository-battle-animations-portraits-map-sprites-class-cards-maps-tilesets-etc/3326/1732
However, I used a different palette. Do you want a Blue/Green/Red umbreon (based on player/npc/enemy)? Which gen of sprites do you want?
Gen 3 uses 2 frames:
You can find these on the Spriter’s Resource website. It’s simply a matter of formatting.
Lastly, portraits should also be easy if you simply format an asset from the games. The Mystery Dungeon spinoff, for example, has portraits for each pokemon.
Good luck!