Please reference the attached PDF for mockups of the two main screens in the game. The design itself is horrible; they were just used to convey functionality to the developer, so feel free to rearrange as you see fit.
The first screen is the game lobby. The basic structure of the app operates similarly to Words with Friends by using a lobby to keep track of games that a player is currently involved in and also to start new games. At the top, a user has the option to start a new game with friends or just join an open game with random players. Below, players can scroll through their list of "game cards," where each game card represents a game they are involved in. Each game card features a preview of the photo that is being captioned in that round to help players remember which game is which. It also displays the photos of the players involved in that game (or any outstanding invites), provides an action button (e.g. telling the user to caption the photo or check in, depending on the status of that round), and gives the player the opportunity to withdraw from the game or block other players in the game.
By clicking on the action button on the game card, the player can hop into any particular game. The second screen in the PDF shows what the game screen will look like. That screen is comprised of the photo that is being captioned and a group chat area at the bottom, so there is only a minimal amount of design needed for that screen. Players submit captions that are then overlaid on the photos, and then players can swipe through all the submitted captions and vote for the funniest.
After each round, a leader board displays the votes from the last round and ranks the players.