I disagree with you on your claim that the art has zero value - clearly the OP saw enough value in it to frame it and put it up on his wall - he saw more value in this than something he could have purchased because it was exactly as he wanted it. The fact that that art piece might have zero market value is irrelevant as the OP never claims to want to sell them.

I also fail to see why it is relevant to point out that the OP lacks artistic skill - it was the vision that was valuable to them; putting a paintbrush to a paper is simply a medium that they were able to circumvent with a simpler solution.