Although suggestions about grouping were mentioned in several ways in different threads before, I'd like to add a short and hopefully precise suggestion.

As far as I understood, present stage is:
Adding a single popup-menu option for some functions and improve viewing functions like zoom and to add a way to group the pics.

For grouping it could be good to simply group by folders and add add the option "group/all" as menu option.
If you solve it this way, it would be easy to add the video-folders as groups and use the video preview pics for it.

Of course there has to be the "open" function in menu.

Folders are allready existent and is the most common way for users to sort their pics.
The "open" functions are standard defined for all file-types. So all further functions would be made by Realplayer for vids and gallery for pics.

So it should not be tooo difficult to program this by using as much of exsisting standard functions and structures of the system as possible.