From Legacy Wiki
Here you can view your Legacy ID cards; it looks like this:
The ID card is for use in forums across the internet. To use it, go to your Legacy ID card page (Sector 1 > The Syndicate) and copy the link on it then paste it in your signature in the forum you want to use it. You cannot use it in Legacy forums.
The image is automatically generated everytime it is viewed, so everyone can see when you level, when you change gangs, or when you get a new cool weapon.