I'm not exactly sure if putting a watermark in the background of the Chairman's is even possible in the format that it must be submitted, though I am not completely certain that this cannot be done. Chairman's Award entries, along with WFA and website entries, must all be submitted at
www.firstawards.org. On this site, your Chairman's Award entry essay is simply submitted as text without any visual design and formatting and pictures are then added separately. You can, as I don't feel this would be a massive issue, still produce and print your own submissions with whatever pictures you wish for use at competitions so as to have something tangible and visually appealing on site to show people and use for promotional purposes. I apologize if I have misunderstood any part of your question or have overlooked the possibility of using a watermark. If necessary, please feel free to correct me. I hope this was of some help.