UPDATE: The site: http://sig.grumpybumpers.com/ is back up! You can still use this site where you can use a Signature Rotator AND Avatar Rotator :
This rotator is also free but you just need to register. Only requires you to use an email, make a username, and make a password. Here is a helpful Youtube guide I found to help with setting up your Signature Rotator:
SignAvatar Youtube Guide
Let me know you if you guys need help setting this up or would like me to add more with the guide.