I think there should be backgrounds for scenes where we’re inside a character’s dreams, not thoughts.
Can you explain what you mean? Because I think you can achieve that with overlays and the correct filters
I’m with @Lxyi could you maybe elaborate what you mean by ‘inside a character’s dreams’?
When I read this question, I just think about what a writer can set up as the introduction and what scene comes after a dream scene(s). Like this:
Before the dream scene we see a character going to bed and falling asleep. The screen zooms in on their head and fades out.
Then it fades in with a new background, the character is somewhere of your choice, where the dream will play. Things happen, etc.
After this, the dream fades out and we fade into a scene where we see the character lying in bed and waking up.
Wherever the dream is: in the park, in a cemetery, at school in the cafetaria or anywhere else, you can use all those kinds of backgrounds as long as you set it up right or end it with a character waking up, if you want the reader to understand it was all a dream.
Now that I’ve written the above, I suddenly think that maybe you mean there could be more fantasy kind of backgrounds? Like magical lands full of castles, mountains, fairydust in the air, etc.? Correct me if I’m wrong though, haha!