I'm no artist but I definitely am feeling the moodiness you've intended. I think the first is the strongest and the sharp realistic trees help. The next four look good but lack a subject for a point of interest. The last one has a focus but could use some interesting detail or a foreground subject on its left half. They'd make great backgrounds for a point and click adventure game!

As for subjects, maybe a silhouetted figure with some distinctive shape would work for the street scene. The harbor scene has a vague oriental feel so maybe a small junk in midground or a massive Chinese treasureship in the distance?