I think that pking is dead because there is just no interest for it, retired pkers probably already have their fair share of seasonal plaques and enough kills to show for it.
I'm not retired but I think to keep new players pking adding another reward system to the mix wouldn't be such a bad idea. A milestone system where when you hit a certain amount of kills you get something to keep you going
(Maybe a hat maybe gralats maybe both)
This has been brought up before by others but since there's a chance for feedback I'm going to say it again.
I'm going to be totally honest I don't think that old retired pkers are just going to come back if something was changed about pk. They most likely quit because they got bored of running around swinging their sword around. It's not the most eventful thing to do in classic.
Sorry I completely diverted this post from its title which is tower rewards, my bad :)