First ideas on my game design

I want to look at a game level which involves a swamp and a desereted castle, so i need to research types of trees, as i want this to be realistic, what trees would you find in an old swamp and what type of castle would there be. am i looking at a particular continent for example...i could use a mexican rainforest setting, and an old ruined temple like that at Palenque, which i have been to i think this would be a green kind of colour scheme, as this was in a rain forest. or should i go for something darker, more european, say like Bavaria or a setting from a dracula film.. or something magical like maybe the film Avatar which was a lot of blue colors or like in star wars... which was more like a real forest but where the trees were bigger with rope bridges etc.. or the cartoon film the rescuers, set in New Orleans swamp with decaying houses all around... do i wnat to put bones into the swamp give a bit of atmosphere. what is the feeling of the level, is it gloomy and scary or is it surprisingly scary? shoudl it start out nice and then change over the course of the level...light day to night i need to give some movement to the foliage too to make it more realistic, maybe moving leaves to imply that something is coming but maybe its just the wind..