I made about 20 textures, which you can grab here (until I need the Dropbox space back). Some of the source photos worked surprisingly well (a blank white wall does gnarly things if you push it far enough), some were obviously going to be great (raw concrete ceiling), and one particular paint experiment completely wrecked my nicest paintbrush.
PART 2: ILLUSTRATION
I grabbed an old piece to experiment with.
With added type, texture and colour treatment:
The way Andrew worked in the halftones was really cool to see—it wasn't part of the original inked piece but it sits really perfectly. I tried to do something similar here, and I'm pleasantly surprised by the results.
I think I might like to be more granular with certain details, so maybe making custom brushes and brushing details in/out would be a logical next step.