New edit - better, but the upper left will probably not look like the lower right due to the distortion correction. I may try a different correction to the distortion.
Jim
I'll re-look at the corner - thanks for the comment.
And yes, this was hanging on a "high, far wall" as you entered and was taken at an angle, and off center. There was another piece hanging in the way. I used some distortion tools in Lightroom to make it square, probably resulting in the upper left being soft. There were two other panels: one left, one right. I could find no artist info, as you could not get close to it.
Another great find for the challenge. The upper upper left corner seem a little soft in comparison to the rest, perhaps a lens decentering issue, or was it captured at an angle?
On a different note, I'm wondering if the artist should be credited in the description. Although if it was displayed in a public gallery where photography is permitted I guess there is an expectation it will be photographed. Just a thought.