nope   if you right click on a file contained in the fly out menu (and not on folder initiating the fly out), there is no options for Dock Entry properties.

using IP will change icon for all files with the same extension. Since it's a film folders, there are all MPEGs but are different movie.

I'm assuming you've created the flyout as a 'Folder'? If so then there's not many options from within OD that can help you. It's not hard to see why - OD is not responsible for rendering the icons in this case, it's just displaying the contents of the folder.

One workaround is to change/create the flyout as a 'Custom Menu' in which case you have to add each movie file manually but you can assign any icon you want. The drawback is it's much more tedious if you have many files. Also if you add more movies to the folder later they won't appear in the flyout automatically - you'd have to add them manually.

Ah ! ok. Well, For the time being, that's a workable solution until next version of OD+ (pleeaasseee !)  

UPDATE : After trying it out, icons stays small to the point I can't figure out what's in there. Why not making those types of flyout menus the same as root menu, i.e. big icons and zooming effect, etc... ?