The solution I used goes like this :
- Copy the folder of your current theme
- Rename the old "default" folder to something else
- Rename the copy of your current theme "default"
A downfall to this is when you update your template or images you have to do it for both copies of the theme.
If possible you might be able to make a symbolic link (a shortcut) if it's a Linux operating system using the a command like :
ln -s .../themes/theme_name .../themes/default
Please let me know if you have any errors.