So if you 'edit' the image rather than 'manage' it you can add it to multiple tabs in the same way as you can add it to multiple characters! ovo
Also, if you want to move an image from a tab via the manage images option, you first gotta go to the tab itself. The manage image page is per tab, and not all tabs at once. It's annoying :/
And other than adding numbers or smth in the tab name, there is no current way of sorting tabs :'(