Hi mate
You can run multiple images on a usb stick under ba all on the same partition the are stored in separate folder.
The main issue with what images you can run is the images you use in BA are of the same kernel type as the Newnigma image in your flash. Now using one with a different kernel type does not do any harm it just wont work correctly error like no tuner etc but try a few you'll find out the ones that work.
Ferret