Horror and Landscape personally, but that is because I find Landscapes a chore to photograph at times so would like to see what you can do with them with your photoshopping capabilities Horror because horror is generally awesome and would be cool to see you create a horror image that isn't just the same old stuff everyone has already seen.
all of them please! i think i voted portrait, but yes, try them all! horror would be fascinating from you. maybe horror-themed portraits? or dark landscapes? it would be awesome to see portraits in your trademark style as well : D
I don't know what conceptual art is so I went for landscape. But horror and dark is only ok if you knit a pink zombie costume and stuff your famous little white hamster into it. THAT I can deal with but I don't know about horror and dark with your style :/ Anyway I'll go google conseptual art now ^_^