Do you have a texture brush and want its texture to be the icon? If the version of Sketchbook you're running supports it, try Use texture as icon in Brush Properties to create texture icons. If you would like to create your own icon, check out Importing brush icons.
IMPORTANT: Sketchbook doesn't currently support using a texture for a brush icon on mobile.
Using a texture for a brush icon in Sketchbook Pro for desktop
You can only use a texture as an icon for a texture brush. If a brush doesn't have a texture assigned to it, you won't be able to use a texture for its icon.
- Double-tap a brush to open Brush Properties.
- Tap the icon next to the texture brush name to open a menu of icons.
- Select Use texture as icon. The icon will instantly change.
If the brush is not a texture brush, this option will not be available.