If your problem is the similar to mine you can visit any OSX 10.8 mac in an Apple Store and accept iClouds new terms and conditions with the Apple ID / password you use on your Apple TV. Photo Stream will then work on your Apple TV at home. It's an easy and free workaround solution.
I could not accept the terms and conditions on my Mac with OSX 10.6.8 (Snow Leopard) or my iOS5.1.1 devices or my Apple TV Software version 5.1 in order to use Photo Stream on my Apple TV.
Visit an Apple Store and find a Mac with OS X v10.8.2:
- Choose Apple () > System Preferences.
- Choose View > iCloud.
- sign in to iCloud with the Apple ID that you use on your Apple TV
- After a moment, the latest iCloud Terms & Conditions should load.
- Read the iCloud Terms & Conditions, then select the checkbox for "I have read and agree to the iCloud Terms of Service".
- Click Continue.
When complete, you should be able to access Photo Stream and related services on your Apple TV.
The workaround solution above is a modified copy/paste of the support Article:http://support.apple.com/kb/TS4425
Apple support UK gave me this insight that I don't need to use my own computer to accept the new terms of service. I asked this savy support rep if she would like to add a note about the solution here on the community to ease peoples pain but she suggested that I do it myself. This is a workaround straight from Apple to me to you. I suppose it will never be official. Note, the computer I used had a guest profile active which allowed me to log out then log in again afterwards to be sure my Apple ID and password would not be compromised.
Good luck with this solution if you want to try it out.