Custom Brushes save a lot of work, you can make them from any photo. I going to use our favorite fiddler.
I open my image of Mairead and then Duplicate my original by going to Image>Duplicate. Then I close the Original.
Next I resize the image by going to Edit>image size. I set my new image size to 1000 by 1500. The brush shape can be any size up to 2500 x 2500 and our image of Mariead was too big.
Next from the previous tutorial I posted about the Quick Mask isolate the area you wish to make into a brush.
You can use this for rocks, trees, grass, houses, castles, etc. It helps if you make the brush rather large like 1000 - 1500 if you want details to stand out at a large size. If you make them too small and then adjust to a bigger size you get a lot of blurring. I will be back later with a tip of how to save your new brushes in a set for those of you who don't all ready know this.