That is the best idea ever.
Before computer days (BC) I worked as a designer in a small design studio with three employees. Frequently we would have catalog layouts taped down on our drawing tables. It was very important to keep these clean since they would later be sent to the printer. Any dirt or mistakes on the pages would mean a lot of work and another trip to the typesetters. So once, actually more than once, I took some india ink and dropped it onto a piece of clear acetate and let it run down. It made a nice splat and a run. I then let it dry and then carefully cut it out with an xacto knife and lightly spray-glued the back of it. Then I placed it in the exact center of one of my co-worker's layouts. It looked super real. When he returned, he was incredulous. "Look at this!" he yelled, "Will you just look at this!" "Oh, that." I said, and then I simply reached over and picked it up. I think he threw something at me.