Ya you definitly need some trees or bushes or something. I too think the top where the columns meet with the building should be changed to something else. Also may be the top part of the columns shader should be changed. It looks almost like you left the default shader on it.
I'm not sure if the column shape is what you want or not, but you may want to remake them. What I did in this picture is take a NURBS cirlce and just pull in every other vertex. Then duplicate and loft.