With Photos for OS X not being released until early next year, it seemed like there would be no way to view your photos backed up in iCloud Photo Library away from an iOS device for Mac customers. However, screenshots and error messages from iCloud.com show that a Photos app is in development for the website, so that users could access their pictures in some fashion on a computer. This will likely act as a stopgap before the official native client is ready.
The above screenshot is captured from an Apple help page, clearly showing a Photos app in the menu, which is currently absent from the public site. The app features the same icon as the Photos app, but its unclear what exact functionality it will bring. Poking around a bit, we discovered something that means it is unlikely the screenshot is simply a Photoshop mistake.