A big mistake many make when trying to create a tileable texture is that there is not enough area in the material to cover a surface. When using a small 20X20 inch scale, which is Chief’s default, the pattern repeat will be quite noticeable.
When you click on some of the brick textures in my selection, you will notice that many of them cover a wide area of surface. You will need to scale the size in the material dbx.
You can see how seamless and real the brick looks.