it seems the brandished weapon would be the E-11 (rifle) with extended stock. The holstered one would likely be the carbine version, and with what appears to be a different scope.
Also, as far the muddied-water between the storm commando and shadow scout is concerned, here's something to help make things clear as mud..
http://starwars.wikia.com/wiki/Shadow_scout
They state, "The storm commandos, also known as Imperial commandos or shadow scouts, were elite members of a branch of the Imperial Stormtrooper Corps."
They go on to say, "They were typically deployed into squads that consisted between three to six commandos. However, in certain missions that were considered suicide, squads consisted only of one or two individuals. They were normally deployed on operations against enemy leaders ranging from assassination to capture missions as well as destroying any important facilities used by their foes. They were even known to take part in assassination missions against a target".
Not that any of these posts should be considered definitive proof or that those who post on this sight are by any means experts, but I do believe it has been used as a reference before (but dont quote me on that).