Hmm let's see.. I'm not the best at these things but I'll try!
Can you guess which of these ponies is from (insert year here)? Since this can have multiple answers.
Which pony do you think was sold in (insert a country here)? This might be a little harder..
If you have the dream castle & majesty maybe you can ask "which pony do you think rules this castle?"
"How many male ponies can you find? / How may boys do you think there are?"
"Which of these ponies is a (insert gimmick here) pony?" This could work for really gimmicky sets like princesses, precious pockets, sparkle ponies, glow n shows, etc.
"Some ponies had to be purchased through the mail, can you guess what one of these ponies might be?" If you have mail orders, but this might be difficult.
Maybe you can ask "This pony is called (insert name) and she has a symbol of a (insert symbol), can you find her?'