I wonder if there's a modification to make it look more like a billboard... perhaps completing the sides and top? Is there a way to do that without losing the cityscape feel?
I like the ladder element in #22... what is throwing me a bit is that it is somewhat "busy" and the other elements, like shrubbery, lose the essential detail in a thumbnail size. Any ideas to fix that? Any other ideas that are radically different to express the notion of Be the Billboard? Feel free to try something new.
I just saw your portfolio... I wonder if there's something to do here like with Male Mettle, where you involve some different colors and add depth/dimension? What do you think about that here?