Users display picture


For my new forum, I wish to set the users picture as their in game face.

The picture itself if generated by another website.

Here is an example of one of the images:

I wish to set the players picture URL as

USERNAME is the name of the forum account.

How would I go about doing this?

I don't want the user to be able to edit their avatar.

I also want to edit the forum page to the user that they must sign up with their in game name, how would I edit the register form?