1. He may be expressing that he misses the good old days, or he is seeking peace and tranquility.
He may be injured and need a period of solitude and self-healing, and the sky represents vastness and infinity, which can make him feel hope and strength.
He may just think that the sky is beautiful and the artistic conception is very strong, and he wants to share this beauty with you.
In either case, it needs to be understood and interpreted according to the specific situation and feelings. If you want to know his thoughts more accurately, you can communicate with him directly and ask him why he wants to set such an avatar.