Nothing special. I just took Chief off the Halo 4 box art and slapped him inside the Halo logo ring. It is a .PNG file so if you can use it for another forum, feel free.
Oh, and I am posting this for fun. I have no plans to re-size this for anyone. Sorry.
EDIT: Here is another one similar to the first one. But this one is just the box art wit h the background faded out a bit behind Chief.