Grease Pencil Material: Stroke Texture Mask

Some brush strokes can look repetitive and uninteresting.

One way to make them more visually appealing is to apply a tiling texture mask to the entire stroke. It's a global texture for the individual stroke textures: unifying them like canvas texture does to a painting.

This technique is used by Blender's Texture Paint brushes (as well as Krita, Photoshop, etc.). Many also allow the user to affect the mask's blend mode, adjust the scale, and manipulate the brightness/contrast.

Here's a mockup for the UI: