It's not that they are hard to draw but I like to juxtapoze real world photographs with the cartoony drawings and if you do it well then you can barely tell and it actually looks like the characters exsist within that space. I did not do this very well in page 7 but I believe page 8 is the best example.
I suppose it could work. You might need to add an effect or filter to make it seem less obvious, but yeah! Only thing is you need to color your people so they look like they belong, such poor lighting conditions and the like.
Well Byberry is a real abandoned mental hospital(was torn down last year) so you could say that the comic takes place in Philly but there are plenty of photo backgrounds in the comic so far, some in Philly, NYC, Berlin, LA and some city in Idaho