Hi Rudy
It's actually quite straightforward once you get the JRiver tagging methods for different filetypes.
Iso files (because they aren't necessarily movie files) are imported as a type 'data'.
So in order to import them and tag them with useful cover art and information you need to do the following:
Firstly, import the iso files into the MC library, you can either do this manually or set up an automatic rule. Both are just as easy, so I will describe what I do which is the automatic way. I save all of my iso files in a folder on my 2nd HD eg. H:\bluray\moviename. So go to Tools->Import in MC, select 'Configure auto-import', Add this folder in the 'Add..' bit, and then 'Browse..'.. Select the 'Disk image files (iso, etc.)' under the 'Video' (or is it 'data'?) heading. I leave everything else unchecked for this rule since I only have iso files in this folder. Hit 'finish' and it should run the auto-import rule. (the advantage of this is if you add any more bluray to this folder it will automatically add the file to MC).
Secondly, for all the iso files you need to change the 'Media type' to Video (and Movie if you wish in the Media Subtype). In order to do this you need to select all of the 'iso' files that you have just imported. You'll find them in the Playlist->recently imported (on the left pane). So once you've selected all of them (Shift-click on the range or just Ctrl-A unless you've recently imported other files) you then need to go to the bottom left to open the tagging pane (Tag). Right click anywhere in this pane and 'show all tags'. Find the 'Media type', click it and select 'Video', find 'media subtype' and select 'movie'. All your iso's will now be in the Video subheadings, but still without cover art or other tags.
Thirdly, the interesting bit, finding the information. Just do this as you would any other movie file, by right clicking etc.
HTH
SBR