So, I cut some moth shapes out of card. I suspended them in a jar, but being able to see in to the jar defeats the point of Pandora's Box... So I moved on.
I went to a charity shop and found an old decoupage box frame. I figured a different way of approaching the idea was not to re-create Pandora's Box but instead present its contents like artifacts in a museum. When I went to The British Museum there were so many monuments and statues documenting figures from mythology (Which is all a bit bizarre really, seeing as it's all fictitious) so I think this approach is quite appropriate.