I found a way you can post your Halo 4 character. You can only use armor you've unlocked, but if you go to your Halo Waypoint and your Halo 4 stats, you can right click your spartan and copy the image url and then post the picture. so If you wanted to make one of them a character, set the armor up the way you want in-game, then hop on waypoint on your pc and grab the pic.

Here I am!
[img]https://spartans.svc.halowaypoint.com/players/iOS%20Jacenater/h4/spartans/fullbody?target=large[/img]

I'm guessing that's similar to what you did, Baku?