FreeBSD can mount most types images. This quick article shows how to mount an iso file into the FreeBSD file system but this same technique will work with almost any image files (as long as FreeBSD understands the file system in the image).
mdconfig -a -t vnode -f /path/to/image.iso -u 1 mount -t cd9660 /dev/md1 /mnt/cdrom
ISO images are read only (just like a CD). You will be able to access the file but not write to the them.
Once you are done you can unmount the files like this:
umount /mnt/cdrom mdconfig -d -u 1