As of Monday, Jan. 21st, 2013 the playlist updates are live and with it comes a new playlist that a lot of fans have been asking for to breathe some new life into the "Halo 4" match making.
343 Industries introduced a new playlist called Community Forge Test and the purpose of this playlist is to thoroughly test these maps for their designed gametypes (Slayer, CTF, etc.) to find any bugs as well as see what players think about them. All you have to do is join the playlist, play the maps, then tell 343i what you think of it.
If you're wondering how can you provide feedback, simply go to Halo Waypoint and go to Feedback thread to supply feedback on your thoughts on each map or go to the Bug Report thread to submit a bug you noticed while playing the map. The ultimate goal for this playlist is to bring community maps into regular matchmaking playlists like Infinity Slayer, thus giving you options other than Ragnarok to choose from. If you plan on giving feedback on these maps, make sure you explain why you like/dislike the map and be constructive. Explaining your opinions will give better feedback to the map creators and ultimately result in a better the map.
If you have a map that you want to be part of the playlist you have to get them noticed by the cartographers. The cartographers are active community members selected by 343i that submit user created maps to 343i for consideration to be put into matchmaking playlists. This originally started back in "Halo Reach" with Bungie, but 343i has picked up where Bungie left off. The cartographers don't take submissions directly from map creators normally, instead they normally look at community sites dedicated to Forge maps like ForgeCafe or ForgeHub. If they find a map they think is good they will submit it to 343i for consideration. Your best bet is to be part of one of these Forge communities if you aren't already and submit your map there and hope that enough people like it that it gets considered.
If you are interested then be sure to participate in this playlist because the more users that play it and the more feedback 343i gets, the more maps we will see in future playlist updates. Happy Hunting.