Microsoft has been promising Chromecast support in the OneDrive app for a while, but only now is it making good. The new v3.2 update includes support for Chromecast streaming of images and videos saved to your cloud storage.
The Chromecast support is the only thing in the changelog, and it's definitely live in the app. And by the way, the OneDrive app is surprisingly solid these days. The design is good, it's fast, and now you can stream your media to your TV.
There's a touch of lag when you start sending photos or video to a casting target, but everything seems fine once you get underway. You should be able to grab the update from the Play Store right now.