If its going to be a small tower with only a couple of soldiers in it, like a safe haven on an isolated farm or an isolated lookout post, i.e. pretty much purely for defense, then the door would normally be quite small - smaller openings are easier to defend against attack than larger openings (unless you want to get large things through it, like horses or carts). There may of course be other outbuildings (farmhouses, barns/stables/whatever) near it that the people/farmers live in during normal times, and they only retreat into the tower to hide or to light a signal flame on the top when trouble arrives.... just some more ideas - my mind wanders to the most odd things during moments of boring meetings ;) Danamo raises some good points about the windows - less, smaller, windows the lower you go is the rule. The texturing looks nice, though the windows (which may just be a temporary texture)... is that a reflection I'm seeing in them, or is it bricks I see behind them.

Dreams are just nightmares on prozac...
Digital WasteLanD