Q: I often put captions above photos that I embed in emails, but I always have this problem: Should it be “Mary and me at the Eiffel Tower” or “Mary and I at the Eiffel Tower”? And why?
A: It doesn’t matter. Either caption is OK.
“Mary and me at the Eiffel Tower” and “Mary and I at the Eiffel Tower” are just verbless sentence fragments.
If you add a verb form, though, you do have to choose between “I” (a subject pronoun) and “me” (an object pronoun).
In the presence of a verb, the phrase could be either a subject (“Mary and I are pictured at the Eiffel Tower”) or an object (“This photo shows Mary and me at the Eiffel Tower”).
We had a post on this topic back in 2009, when a reader questioned a caption in a photographic memoir by Gore Vidal.