Hamburgers are slightly easier to decorate, I think, because you can make cheese slices into pumpkin shapes - and even carve the meat pattys into bats - "Bat Burgers!!"
Hotdogs are a bit trickier, unless you decorated them with cheese slices cut into shapes with Halloween cookie cutters? Orrr you could somehow make the sausages look like fingers and have ketchup all around the bottom and make the buns look like they are oozing with "blood". You could call them "Frankenstein's Franks"
OK actually, I might do those two ideas myself lol!!