There is no direct support for mounting images right now, but there are great ways of acomplishing what you want. I use Deamon Tools, and set it at auto mount, and I set Windows XP to auto play the DVD from that drive to J River Media Center 13. When that is done, you have to actually import the iso, img, nrg files etc to the library. This files will be imported under the Data section of the library. You can either add the data file types to the Video view scheme, or you can edit the Media Type tag to Video for all the image files.
This have at least worked very good for me. I only hope there is a way of setting the Media Type automaticly under auto import soon.