Here is a list of all the avatar/profile backgrounds that is currently available in the game. You can choose to buy them from the shop for 200 gems, they keep changing every 24 hrs. This list is helpful in case anyone wants to choose and wait for a particular one. There is no particular rotation to them, they appear randomly, so make sure to check the shop often.
In case, I missed one or a new one is released, please let me know here and I will update the graphics accordingly.
Updates: 27-Dec-2019 - Added missing Lush Plains