russian prepositional

Alrighty, so this is a bit of a beginner question...

if I want to say "I have in my kitchen white walls" would everything after "in" be in prepositional case or nominative case? I'm reading a bunch of descriptions and the nouns are all in nominative and it's confusing me : ( I know prepositional is to indicate location but I'm wondering if there are any confusing exceptions in Russian I am not aware of? Thank you..