A long time ago i searched a tool to mount cd-images like .MDS .ISO .CUE with linux. There was none... only things like mount -o loop were avaiable.
Today i've found cdemu: it does all i want, it only installs a very small kernel module to emulate a Virtual (SCSI) Host Bus Adapter, the rest is done in userspace.
There is also the small GUI gCDEmu to "mount" an image. It is a gnome-panel applet. Thumbs up! :-)