GET /search/photos adds support for orientation, dominant color filtering, and relevancy vs latest ordering:

param Description
order_by How to sort the photos. (Optional; default: relevant). Valid values are latest and relevant.
color Filter results by color. Valid values are: black_and_white, black, white, yellow, orange, red, purple, magenta, green, teal, and blue.
orientation Filter search results by photo orientation. Valid values are landscape, portrait, and squarish.

GET /collections/:id/photos adds support for orientation filtering:

param Description
orientation Filter collection results by photo orientation. Valid values are landscape, portrait, and squarish.

GET /users/:username/photos adds support for orientation filtering:

param Description
orientation Filter a user’s photo results by photo orientation. Valid values are landscape, portrait, and squarish.

GET /users/:username/likes adds support for orientation filtering:

param Description
orientation Filter a user’s likes by photo orientation. Valid values are landscape, portrait, and squarish.