The more I think of the Imperial Officer with the cloak the more I believe that he is Imperial Intelligence and not some Grand Admiral salute.
The argument is that Grand Admirals wore white uniforms, but they're not Canon anymore.
This uniform
More represents the uniform of Wolf Yularen who was a character from the Clone Wars that was borrowed from ANH where he was a Imperial Intelligence Officer on the first Death Star
Personally while I doubt its true, it would be funny to link the Clone Wars with a fairly major character who was a hero in the Clone Wars in Yularen, who later showed up on the Death Star as the villain pictured.