One thing that bugs me most about alot of the movie posters that i'v seen here is the full white text on a full black background. Its exactly that that makes it look amateurish, imo. If you make a poster and want to use white text, set the opacity to 80% or so, let it blend a bit with the colour of your background. I dont think i'v seen much actual film posters with this black and white contrast.
The fact that the image doesn't cover the whole poster is also not really helping. Add to that that your image is already scaled up and doesn't actually work on this resolution, I wouldn't really put this out there. Maybe wait till after the shoot till you make a fullsize poster. I think the image at its current resolution would make for a nice timeline-cover-photo-thingy, just tweak the text a bit so that its side to side. And maybe add some texture. Personally I find that even a bit of texture overlaid at a 10% opacity with a nice blending mode can make a whole lot of difference, and make your poster look richer and more mysterious.
A good example of both texture and text opacity is this
, although the text opacity is quite low (they actually go for the see-through effect, rather than just colour blending) it does give an idea of what im talking about.