Hi stellarpower!
I haven’t really messed with floppys or floppy images (or that much with images in general), so I just googled and downloaded a bootdisk image. This mounts with “mount CDBOOT.IMG /folder”, though only read-only. “mountvolume CDBOOT.IMG” does it writable. It even mounts writable on doubleclick after setting the filetype BFS Image (application/x-bfs-image).
Maybe your image is corrupted? Or the filesystem is not supported?
Regards,
Humdinger