I basicly did the halloween stuff together with others anyhow all we did was use images.
vines.png vines2.png and vines1.png.. combined with pumpkin images wich are all property of UN. So I won't help you in that area.
Just try to be original and you don't need a whole new tileset
fashion.nw on UN is still a level wich used the tileset thing I did together with shawn64 last year. Its basicly a collection of some pumpking shaped floor tiles but thats it.
Just create your own level and use some swampy elements together with some light effects for steam/mist and some barrels/vines and other stuff and a halloween ish level is born
