Something like this - not quite as pretty, but my Photoshop was being balky:Adding hatching as a textured outer glow or bevelling doesn't seem too hard. So less of a "brush" and more a layer with specific properties.
Quick & Dirty Dungeon Maker
For those wanting to try at home, the recipe is as follows:
1) Get some blue graph paper graphic on a layer
2) Duplicate the blue graph paper layer and (using layer adjustments) make it black and white
3) Now create a layer mask and fill it with black so that the black graph paper is hidden
4) Add 2 stroke layer styles:
4a) a solid black stroke outside the layer
4b) a patterned stroke with the crosshatch (grab a cross hatch from wherever)
5) Set your foreground color to white
6) Select the mask not the graph paper layer
7) Draw in the mask, and voila!