Ok i see. so, if the problem is the rendering time and backgrounds require time as well.
so, to make it faster maybe a phone could be added.
with a default background and him looking at the phone, like:
we could use the phone to read and send text and also receive pictures.
pictures that we can also look again (whenever we want) in the gallery.
the background inside the phone is not that important, u can make it a bit blurry,
and use a "layer" method, u render her and "merge" the pictures together.
the phone could be used for a lot of quests. i would love that!
another thing is using a computer, "webcam", she at school u at home
and u can talk to eachother, and also do "dares", where she can get caught. here u can add levels, from just talking to more sexy time. should be slow progress. but i also think that webcam should have its own "level" , the same with phone. so the player can choose what to focus on.