Here's a hint that might help you with publishing of black&white panoramas:

Due to a bug in the converter that we are trying to solve we are currently not able to process pure B&W panoramas. This bug is not directly in "our" code but in the code of a tool we are using to process panoramas (as far as I know).

A workaround that works: Try to saturate the image just a tiny bit, so that for example gray color is not gray, but e.g. red-ish, or blue-ish. It doesn't need to be visible, if you make 127,127,128 instead of 127,127,127, nobody will notice.

I've also added this to the known issues:
http://help.360cities.net/known-issues