In The Legend of Zelda: Tears of the Kingdom, the stables scattered throughout Hyrule serve as havens for weary travelers and their horses. Link can seek respite by renting a bed and engage in various horse-related activities by visiting these stables. These stables also offer side quests that allow Link to assist the residents with diverse tasks such as investigating sightings of the missing Princess Zelda.
Additionally, he can also undertake a series of quests focused on enhancing the stables' interior ambiance through the inclusion of paintings depicting the stunning landscape of Hyrule. To access these quests, Link must clear any one temple as part of the game's "Regional Phenomena" main story quest and acquire the Camera. Without meeting these requirements, Link can still interact with the photo frame, but the stable keeper will not offer any quests.
A Picture for Riverside Stable Quest Walkthrough
“A Picture for Riverside Stable” starts inside Tears of the Kingdom's Riverside Stable located at coordinates (0328, -1085, 0009) in the southeastern corner of Hyrule Field, alongside Hylia River. There is an extremely close shrine, Tajikats Shrine, that players can fast-travel to if they have it unlocked. The stable is also easy to reach by traveling south of Lookout Landing, or by gliding directly east after launching from Hyrule Field Skyview Tower.
Inside the Riverside Stable, Link will find a large frame mounted on the right wall of the interior. Interacting with the frame will cause the stable keeper Ember to pipe up, explaining that the Stable Association has provided each stable with a large frame in which they should display a painting for the patrons to enjoy.
Ember has his mind made up and tells Link that he wants a picture of a Great Goddess Statue. These statues are already important destinations, as Link can visit a Goddess Statue to exchange Light of Blessing, received by completing shrines, to receive upgrades to his heart containers and stamina wheel.
Great Goddess Statues are significantly larger versions of these monuments and require a bit more effort to locate. Thankfully, Ember has a lead on the location of one, telling Link that he should be able to find a Great Goddess Statue in a temple southwest of Hyrule Field.
He is referring to the Temple of Time Ruins, located at the approximate coordinates (-0794, -1829, 0087), which the player can reach by traveling south to the Great Plateau. The Tadarok Shrine is the closest shrine for easy fast travel, or the player can teleport to the Hyrule Field Skyview Tower and launch upward to glide toward the Ruins.
Once at the Ruins, the player needs to head to the largest building at the southernmost point of the Temple of Time Ruins. Here they will find the Great Goddess Statue, located at coordinates (-0823, -2029, 0119). The statue itself is not functional until another quest has been completed, but Link can take the photo for “A Picture for Riverside Stable” without having completed that quest.
The player needs to aim the camera viewfinder at the statue and ensure that the text “Temple of Time Statue" (not "Great Goddess Statue," as players would expect) and the red quest exclamation point nearby pop up in the frame. The player just needs to snap a photo of the statue and then head back to the Riverside Stable. Ember will give Link 1 Pony Point and a dish of Energizing 
Crab Stir-Fry.
The Legend of Zelda: Tears of the Kingdom is available now for Nintendo Switch.