I did think that there might be something to the thickness, which led me to consider a possible code 128 mini-key barcode being embedded in some way. After failing to generate any functional barcode from this, I gave in to the notion that the brush strokes look like they were applied pretty quickly (or hastily for lack of a better term). When I watch my wife paint, she gets pretty into it sometimes and can get going pretty fast. It creates quite a bit of irregularity and similar looking brush strokes. So to me it seems more reasonable to chock some details, like this one, up to artistic flow.

I am probably wrong about why I am wrong. I have not come up with anything that I have solid confidence in.

In regards to the brute forcing, I agree after giving it more thought. If there was a significantly smaller number of possibilities and I had more confidence in the idea, though, I would not consider it brute forcing.