Try to vary the size of the windows and log rectangle this should help.Also you could try to put some buttons on the logcrossings as "Nails" : D
You could try to extrude some of the window areas so it looks like a closed balcony.
You also could add a small "band" between the diffent floors. something like this for example:
Honestly the size of the windows were there because I couldn't find other ways to make it look good xD. I might mess around with it again.
As for the band thing, that sounds like a good idea. Just that I couldn't imagine my house being quite tall xP.