Okay, I can tell what you were trying to do(Make Gretel's building and use his style). But you dithered and put random pixels in it, which I think would ruin it unless you size it down. Gretel just used the Noise command to make all those random pixels that made a gray wall. I would suggest redoing the whole thing, adding shading to it, better line art(Like a better shape), and use a beter reference picture. The windows arent all that great either, they look too big for it. I suggest taking some tutorials first too, like MonkeyDidIt's tile set tutorial.