As far as hard disk images, I don't think they can be changed on the fly. And I'm not sure if ShapeShifter even supports floppy disk images. Have a look at Basilisk II, which might have those options.
It reads real mac disks 720K formatted by the emu and 800K from crossmac.
Also PC disks and mac disk img files supported.
You through them in a mac partition and when you double click them they just automount on desktop.
