Some shields would work better in certain situations, like a tower shield being useful against archers and dragon fire as it is typically large enough to cover most of your body. Other shields like a buckler or a hoplite shield would be better for a close range skirmish. and what better way to slay the hordes of undead than with a heater shield like paladins of yore? Basically what I propose is they add a few different shields that would have different advantages and disadvantages like they do with swords. They are already way under represented and are getting an overhaul as far as blocking so why not?