Separate Background Images from Sounds.
Create a new area with a customizable list of setups. Through the menu new setups can be created or deleted. On each setup you can customize your sounds as now, but can also customize your background image without needing to reset sounds.
So in the list you could have 'My Daytime Theme' with a sunny picture and uplifting sounds. Then you could separately create 'My Nighttime Theme' and have a darker image, quieter night-time related sounds. The Theme is no longer tied to a specific picture.
Nanette M. Dreher commented
O yeah.... You could call them 'bugs'. And have diffent colored lighting bugs so you would just have to go to witch ever 'bug' you wanted for that moment. Bit limit it to like 3 maybe 4 'bugs' (to many options take away from the nice and neat feeling of this app..... :-)
When you save a profile (see most popular request) you should assign a background so that you can load your new scene by visually browsing the screenshots if you like... Though i think a lot of profiles would end up using the same (classic) lightning bug background.
Having personal themes that you could save is a great idea. I'd like to add if it doesn't work as an "area," maybe it could be implemented as its own "pack." So for example instead of "Jungle Pack" you have "My Pack" or something, with "blanks" that you could customize with images, sounds, and titles.