The sprites are taken from pokemon showdown. As seen by the link below
generally if you change the pokemon name to something else it should work. when entering them into your sig you need to have each one entered as an image.
Started this morning.
Right now hanging out on route 2, I got lucky with my Scorbunny's nature as it's a natural one. I also caught a modest Blipbug so that's great.
I had a corgi named Lacey and she passed a few years ago.