Some Lolita Holiday Costume Ideas:
Witch. Even though it's been done to death! You can put a twist on your outfit, a small hat, or a large hat. Theme it with colors or make a theme.. example The Witch of Candy, The Witch of Cats, etc.
http://www.etsy.com/shop/hatandmouse?ref=si_shop --- she has some cute hats for sale.
Doll. Another one that's been done to death. Heck, Lolita is based on dolls. But there are different variation of "dolls". You can go creepy with an evil doll with a cracked face. Or based on the dolfie look you can draw joints on your joints. A skeleton doll. A crying doll.
..........Which brings me to the next "idea". I put it in quotes because it's not an idea it's more like one of the reasons why Lolita is the way it is.
Alice....... enough said.
Fairy. You can make a pair of small celofan fair wings, just check out these youtube videos. They're cheap and easy!
https://www.youtube.com/watch?v=pTAqSAqZjY4 Princess. In my opinion, there's already an official Lolita category called Hime but jazz it up more! A bigger crown? Or you can base it on a Disney princess. Either way someone will still call it a costume. Am I right?
A Lolita Murderer. Based on the Guro idea, I just like the idea of a cute little girl killing for some treats or for fun.
HORNS. Since horns are very in and I see them in alot of people's coords, why not a demon Lolita. It can be the creepy cute based on Pastel Goth, using demon horns. An elegant demon. A dark gothic demon.
Or elegant "deer" or "faun/fawn" antlers, just slap a pair of antlers on and there you go.
More ideas will be coming soon, these are just the basic kind of popular ideas that I can think of.