The update was announced via the official Borderlands 4 website, and it isn't just a Photo Mode being added. Harlowe's Zero-Point Action skill is getting a rework, and Ultimate Vault Hunter Mode levels will now increase dedicated loot drop levels. But Photo Mode is the crown jewel here, and it's available now by restarting your game and downloading the update. Once the update is installed, you can find Photo Mode in the Pause menu while you're playing. Entering Photo Mode will also pause the game entirely in single-player mode (sorry multiplayer folks, just doesn't work that way).