Low poly Textures

Hi everyone, I just started trying to do lowpoly models, I want to do a simple videogame, and because of my computer and the game it will be easier to run for it. So I was looking for tutorials and I find a lot, very nice, but I didn’t understand very well the texturing and material. I try to use only one material in an object (its what unity manual recomend) and add textures, the textures are like this:

Usually when I unwrap without seams the UV maps are just squares, but when I try these that didn’t happen (maybe because I unwraped a plane) anyway my question is how can add more detail using this kind of texture, like the roof or bricks or some damage (I don’t know the word in english, is a “grieta” like a little earthquake). Here I put a few renders image of the house and the image in what I inspire to do it:

The tree doesn’t have a texture, I just change the material color, but it will be great to add some simple detail with simples textures, like the first that I put. I saw these technique in Jayanam youtube channel, he explain how to apply, but he also has very nice and simple details, but he doesn’t explain how to do it (or I didn’t understand, english is not my first language)

http://img.viajeauruguay.com/calle-de-los-suspiros.jpg (in this link is the picture that work as inspiration for the house, also the post say that I only can add three images, and I have only 2 :confused: )