To use PhotoWall, you must first download the application to your iOS, Android or use a computer with a supported browser and initialize a session. This will then allow you to share photos to your TV or computer (where Chromecast is not available). If you'd like you can send a code to your friends and have them join your session so they can post photos and add to your collage. Those in the PhotoWall session will have the ability to draw doodles, upload photos (supported formats include .jpg, .png, .gif), and also remove content they have uploaded. The host will have the option to manage all of the photos on the collage and can remove any photos uploaded to the session.
Lastly, PhotoWall will create a YouTube video of the session which will be uploaded to the hosts YouTube account. The video will be initially uploaded in private mode which the host can then set to public if they desire. While simple, Photowall is an interesting experiment by Google to showcase the creative side of the Chromecast.