I was once in the same situation and had to resort to something totally different. Have you ever seen those coupon books that you give to a mother, father, or friend on a birthday? I took that idea and applied it to prizes for bingo. I made a bunch of cut out coupons that had rewards, ideas, events or things they get to do. For example.. "Everyone has to tell me something nice today that walks by me", "I control the remote for a day", "I get to play my music down the hall", "I get to help in the kitchen", etc...really though you can base them on activites that you are doing in the week or allow special deserts. I would always like the special reader and singer in your room coupon. Hope this helps and gives you some ideas that can make it fun to incorporate different staff and activities!