Neat! Never seen a Diana reverse with the bow drawn, must have been too much effort for the celator.
Valerian was the only clear-cut example of an emperor killed in Captivity, but in my mind, there is another: Majorian, the last great emperor of the West. His rule marked a great improvement in the Western empire, with many reforms aimed at restoring Roman glory and stemming the rot. By this time, Rome was falling into disrepair and many of the great monuments of the city began to be used for building materials - he stopped this by chopping both hands off of civil servants who allowed this to happen (though the judges that ruled in favour of the quarrying got away with a measly fine of 50lb of gold). He secured Italy, recovered much of Gaul and Hispania and probably would have campaigned in north Africa if he had the opportunity. However, his activities went further than just restoring the city - he also had a mind to stop corruption and restore proper order. No longer could the aristocracy avoid their taxes! This, of course, didn't make Majorian any friends and a plot was hatched against him. Majorian was travelling to Rome (this would have been his first visit to the city during his reign) to meet his magister militum, a german named Ricimer, but Ricimer had other ideas; he took a detachment of soldiers and arrested Majorian en route, seizing his imperial diadem and stripping him, followed by severe beating. He held the deposed emperor captive for 5 days before finally lopping off his head; 3 months later, he would proclaim Libius Severus as (puppet) emperor, though Leo I in Constantinople refused to recognise this appointment. Now, some might consider that an old fashioned usurping, but in my eyes, it is something more: Ricimer was the son of a Galician king and grandson of a Visigothic king and his sister married the Burgundian king. His blood was filled with hundreds of years of anti-roman sentiment and his thirst for power once saw him attempt to dissolve the Western empire (as a German he could not be emperor, but if it wasn't an empire, that wouldnt be a problem). In my eyes, Majorian's death is under captivity by the hand of a barbarian...even if that barbarian had great power and a roman title.