I think you need a higher resolution texture map, since I can see it has been repeated for many times (or just apply Unwarp UVW and start 'painting' there). Other than that, you should give some displacement/bump to the roof tiles so that it will not look like 'paint'. It will be nice if you put some 'drawing' on the windows, just like in the church/cathedral in real life. Adding algae on the parts near the floor and the 'necessary' parts also will make the scene looks more realistic ;) For the bricks, I think it should be greyish so that it looks 'older'. When you render the 'final scene', you can do an ambient occlusion pass, then the different light passes, shadows, reflection, refraction, GI etc so that you can have more 'control' over it.
Here is a tutorial about that :
http://evermotion.org/?unfold_exclus...fold=exclusive