Good news! 343i is updating Flood with three community Forge creations: Black Site by The Fated Fire, Malice by AgentPaperCraft, and Serenity by DG Intensity. I've already seen two of these maps featured on respectable Forging channels, which means the maps must be pretty good. This is the perfect present for my birthday. Also updated with new maps are Rumble Pit, Team Objective, SWAT, Team Snipers, and Infinity Slayer; I'll see you all in matchmaking!
Source: http://halo4nation.com/news/halo-bulletin-5-2-13-map-updates/
(links to map showcases coming soon...)
ForgeMonitor's post in Update Flood Playlist was marked as the answer