Are there unviewable flying / dark / steel type backgrounds in Pokémon Go?

Since the Generation II release, the "Dark" and "Steel" type backgrounds were added to the mix, and "Flying" was added with the release of Tornadus

Steel

Dark

Flying

Through game datamining, I have been unable to (as of yet) find any semblance of backgrounds for any of the Dark/Flying/Steel backgrounds.

However, knowing Niantic and their method of operation, they likely do have these assets ready (but not packaged in the game yet), but are just waiting for them to become useful -- as in, there actually being Pokemon of primarily those respective types.