I figured out how to add my own toons picture to the forums, and as requested, I added his website to the signature, but I still cant get the picture to come up for the signature. I have an idea for reviewing Foundry missions. Check out the Meowbox for details.
I don't think you're doing it correctly - if it is in your signature, it should show up automatically on all of your old posts. I only see it in this latest post.
Go to forums index -> User CP -> Settings & Options -> Edit Signature. If you put your link there, it will properly show up in all of your posts.