Already have the window, could put this on one of the tables when you first walk into the barn. Maybe next to an old suitcase that i have with burlap banner saying either "cards" or "advice" and guest can just drop either cards or advice in the suitcase
30 Creative Ways To Reuse Old Windows | Daily source for inspiration and fresh ideas on Architecture, Art and Design
In Plain Sight Give an old window new life by turning it into a rustic cupboard. Construct a three-sided box to fit the window. Install shelves to align with the window muntins. Then attach the window to the front with flat hinges. Now you've created nooks to display pottery and other treasures.