I edited the piece quite a bit, hope it looks better now :)

I agree totally with ensellitis, the dark "l" pixels make your piece look boring because they look "pattern like" and confuse the viewer.

I like the layout and design very much. I think this needs a stronger lightsource to add so interest. Ensellitis suggestion will go a long way to do this. I would also suggest moss/aging in areas since its very even in coloring throughout now. The rooftops are very bland and seem unfinished. Some overhand of the tile roofs are highly recommended to break the "shapes" up. Good job, tho

try removing alot of the dark lines on the bricks, the ones that go like a "L"

they look to repeating and make the castle look too dirty.  try either remving them or making them much lighter.  the front section that does not have them looks great.  nice castle :D