Well this is a tuff one for exposure, and actually think you handled it very well.. something has got to blow when shooting into that light...
I'm mixed on the angle of the shot, but understand why you chose it, in order to show the face of the painting... Was curious if you had any more lens left , or why you didn't back up just a bit to include possibly more window , ( wall to left ) and also show entire painting frame ?
Now don't get the wrong message from above, I think this shot is very nice, and I to enjoy your take on this...