This could be a lot of fun! How about "Spooktacular Birthday Celebration!" I'm sure you'll get a lot of goulish suggestions-just crank out some creepiness and get on with the eerily delightful planning.
Instead of having a lot of princesses show up- invite guests to wear their costumes. Bobbing for apples? One game I used to love was called something like "VAMPIRE" everyone playing was blindfolded and set loose in a fenced backyard with one person having been chosen as "IT". Everyone wonders around. Anytime the "IT" bumps into someone they grab them and yell "VAMPIRE!" which makes that person a vampire too. If too vampires bump into eachother they become "normal" again and if two normal bump into each other they stay normal. The game can end when everyone is a vampire or in a strange twist-it can keep going if two vampires become normal from bumping into eachother... The "IT" becomes normal again when grabbed by another vampire. It's a lot of fun especially in the dark and because you're blind folded you really freak when someone suddenly grabs you and yells vampire. Usually everyone yells or screams. LOL Lot of fun too for giggly girls with crushes on boys. The "grabbing" amounts to a hug which of course is fabulous to those teens. The blindfolding is supposed to help prevent cheating (a parent or guest can supervise) to prevent cheating or inappropriate touching which was never an issue when I played it but is a consideration nowadays.
It's not a typical game played by little kids-because little kids get scared and don't do well sticking to rules for so long.
How about an orange cake with black frosting? Or vice-versa? Jack-o-lantern decor-with 16 carved out instead of creepy face? Black and orange crepe paper hung up like for Birthdays. If you daughter is fond of cats-use black cats-cute ones or halloweenish ones...Depends on how far your daughter and you want to go with it. Is it to be creepy or cutsey since it's the sweet 16? Talk to your daughter and see if she has any ideas herself. She might surprise you!
Consider playing creepy music in the background. JUST listened to a great-music only-creepy soundtrack of shows and scarey movies from Target. It'd be perfect to set the mood but allow the guest to talk and laugh and not interfer like moster mash and one eyed one horned pied purple people eater which of course, you could also go with but that gets cheesy when it's stuck in your head or you try to talk over it.
Another idea, keep the house dim and use candles for light...
Hope that helps. Above all-have fun & enjoy it. She'll only be 16 once!