You edit the /etc/sudoers file using the "visudo" program. The file has a commented line with an example for mounting a cdrom. You can base your entry on that one. If you are on a remote location, you will need to ssh into it before you mount the image. I don't know how well it would work to mount an image that is accessed on a samba share.
One other option is to include /etc/fstab entries on the server and mount them on the server. You could offer the directory used as the mount point as a samba share. It would be as if you were sharing the cdrom itself, only it's just an image. I keep my install dvd image on my laptop.
There is an /etc/fstab entry for it:
/suse/openSUSE-10.3-GM-DVD-x86_64.iso /suse/suse iso9660 ro,loop,defaults 0 0
I have this offered as a guest share:
path = /suse
guest ok = Yes
This share could be used as an installation source on any other OpenSuSE10.3 64 bit distro on the lan, meaning that a disc isn't necessary if I want to install another package for my desktop.
Being an iso9660 image, it is a readonly filesystem so it isn't possible to change its contents. If the directory on the server share contains just images, you could offer the mount points as services instead of the images themselves.
Doing this, you would need to mount them manually the first time, but afterwards they would be mounted if you rebooted and you wouldn't have to bother. From another computer on the LAN, you would just need to browse the service to access the contents of the image you wanted.