They were on the old site as well and they are badges that showed up under your Avatar on the old site to say you had lost half century(50lbs) or a century (100lbs)...there is also one for maintaining.
The Century Club forum is under the Wemitts section.
In the meantime you could have a look at Glitter Graphics as they have a selection on there that might suit you to add to your signature...you just need the bb code and it will show up like this one I have looked at just now. If you click on it, it will bring you to their site.