Our county show is always right around halloween so we do a costume class. Kids put hats and fabric drapes on their calves and there is always lots of glitter, just DON'T use adhesive of any kind, plenty will stick with nothing at all. One year I had a heifer that you could not scare with anything on this earth, so after the show we did pictures on her back or standing with her (she was tied with me holding the kids on her back the whole time and between her and the people standing with her no matter what. We charged a dollar and made over 900 dollars through the week with her alone. I would check with the people who run your facility about this first and also with your advisor/4h leader beforehand because there is a lot of potential liability in that and you could possibly end up on the bad end of a lawsuit if something does go wrong and your calf hurts anyone by some freak accident. I would say your best bet is to let people pet her and any other calves that are gentle enough (and their owners are willing) and charge a dollar per calf that they pet or 5 to enter the barn or something (pop) (pop) (pop)