Sharing custom made game levels with other users during gameplay.

I am building a game where users can create their own levels from sandbox and share it with other users for playing. Something similar to this scenario,

Say game name is Image Puzzler.

User A: Creates a puzzle using her own photo and wants to share it with User B. She wants User B to solve the puzzle and view the final photo.

User B: Loves this concept of creating own photo puzzle game. She decides to share her own puzzle photo with all the users of Image Puzzler game.

I am pretty sure I would need servers to identify users and share data, or is there any straight forward way to achieve this? I am also clueless about how the puzzle data from User A be passed to User B. Could someone help me with right pointers. Thank you!