If you are interested in making a number of Themes I would suggest that you make a Theme called Template.zip
---
To create such a Theme go to Default
Type in you all your Custom Appearance Settings as well as your preferred back cell image.
The Theme you are in now will have become Default*
Rename default* as Template and Export.
That will give you a backup copy.
From the moment you have made Template, just enter Template, load in a new background, make any other changes you deem necessary, rename the Theme with rename and save.
This is very quick.
---