How would I do this?

[MahdyE23]

Hey guys, is there a way to add something extra under the avatar? Like for example, how it says this:

http://prntscr.com/13wql7

I have a server and I want to add something called "In Game Name" so people can post their in game name and it can be visible under their avatar along with their posts, etc. I only figured out a way to add it in the "About Me", only I don't want it there. I want it here:

http://prntscr.com/13wql7

Is it even possible?

I want to end up making it look like this:
http://prntscr.com/13wr6g

Being able to add "IGN" and stuff. How would I do that?