Here are some nice galaxy Pokémon.
This is a galaxy Lycanrock. It used a pastel galaxy background for the Lycanrock, and some blueish-purple for the background.
This is a galaxy Lucario. For this one, I used normal galaxy background for the Lucario, and a coral-colour background.
This is not a galaxy Pokémon, but it took the same amount of effort. It is a Combee.