You're missing something here Julia, something on a more fundamental design / drawing level. What emotion are you trying to embody in your designs? All of the things you've listed are just generic descriptions of objects...where's the emotion? Look again and you can see it - For example 'Nostalgic / Past + Native American' or 'Romantic + Waterfall'. Design is language, get your words right first and go from there.
https://www.youtube.com/watch?v=U9RBe5Ie12cGo to 10.10mins and listen to how this guy describes his environment as 'beautiful decay' (note don't design anything post-apocalyptic just listen to this as an example).
Also, take a closer look at why you're using words to describe an environment. For example is you say 'Nostalgic + Native American' what colours are associated with the word 'nostalgic' and what colours are associated with the location of 'native American', what time of year, what decade etc.
Are you referring to - as an example - in terms of the colours used in the native american picture I have here ''Warm Yellows'' ''Desert Yellows'' and ''structures that look worn, travelled and dusted.'' As a way to describe the environment and the colours associated with it?
It's all of those things...however the person who painted/made it planned all of that beforehand. He/she knew that nostalgia or 'old world' was going to be their palette.
So what am I really looking to do really? (sorry for the really late reply been very busy of late). I want to build an environment but I'm still not very sure what environment I want to make.