You've added shadows(?) all around the lineart. What's your reasoning bahind this? Wouldn't it make more sense for some of the brick's sides to be in shadow instead? Choose where your light source is, and the sides facing the light would be lightest, the sides facing away from the light would be darker.
I'm a total newbie, I'm drawing mostly because it's fun for me. Thanks a lot for your comment, I shall pay more attention to shadows next time :)