"If you would like it, please tell me your phone number and why you want the picture. After the item is given away, I will delete all correspondence that comes to me.... I ask for these things to determine whom I will invite to my home for my safety and that of my family. Thank you."
Some possibilities:
"I want it to record for posterity how little was required at the beginning of the 21st Century for something to be designated 'art.'" [threat level - uncertain, what does "posterity" mean?]
"I want to use it as a coaster. I am 28 feet tall and drink from three-gallon cups." [threat level - surprisingly low, 28 foot tall people are easy to spot and apprehend]
"I will shoot it. It has a bulls-eye quality to it that inspires the marksman in me." [threat level - medium, has guns, but is accurate]
"It's beautiful. I want it to make my home a more aesthetically pleasant place to live." [threat level - high, is insane]