well tracking down the "copy" option from the drop down menu is impossible, but you can disable right clicking (but they can always use view -> source), or track it, although it will be inaccurate. for an example, i right click on images all the time to open them up in tabs (although you could have a script on the page it goes to to register if they did or did not open it up in a tab, although that gets complicated)
but yes, you could have a trigger only for a certain photo, just register the onmouseclick with the thumbnail, not the document. here are some helpful links:
Registering the Right Click
Ajax Solution
Ajax Solution