One of mine was actually terrified of camera's and mobile phones so polo's were placed onto camera's and phones until he realised neither were going to eat him. Ever since that point I got nice photo's of him and even if his ears weren't pricked blowing a loud and long raspberry always did the trick, you need to pick a noise they aren't familiar with so it grabs their attention and you can't be shy
When I'm judging the photographer usually has either a bunch of keys that jangle or get tossed, or something like an old film container with something rattley in.
Professional photo/video type here, do lots of horses!
Throwing grass, clicking, rustling, always seem to work quite well. Whistling sometimes works too. I also sometimes find the click of a shutter gets the ears forward in itself, so the first photo can get binned but you still end up with ears forward
Feed her some tic-tacs but rattle the box before feeding each one so that she learns to associate the rattle with a treat coming. That should then work for the ears....
I would go for the carrot or large visible piece of tasty food.
The noises and sudden movements get you ears forward but you also get "worried" eyes with little wrinkles over them. Can't stand to see that, it spoils a pic for me more than ears back!
I had most luck with someone holding an unlit cigarette - I guess they must smell quite strong but still a natural 'planty' smell, got some really interested expressions from that!