I make use of the Ark module by @Daniel_KM so each new item automagically gets a persistent identifier (PID) in the form of an ARK. Works like a charm!
Dutch policy on digital heritage states that each information resource should get a PID. In Omeka S terms: both items and media should get a PID. I think the Ark module could be expanded to also associate new media automagically with an ARK.
) but the feature request can be discarded as it is already possible via configuration of the 