i copied copied and pasted this post which answers your question
apollo2626 Nov 22, 2013 8:16 AM
Thought this might be helpful to have posted here! I'm keeping a list updated for my clan members and figured other clan leaders could benefit from it! Feel free to link back or copy any part of this! If you find any updates please respond to this post! I'll also be keeping the copy on my clan's news feed updated daily! Hope it helps!
How to Earn Call of Duty® Ghosts Clan XP
Play any Online Multi-player Mode with At Least (1) Clan Member:
Participate in Clan vs. Clan Playlists that requires (4) Clan Members:
I list all the unlocks on that page that I'm aware of so far. Some we don't know about quite yet as no clan has gotten that high. The highest clan I know of that I'm tracking is level 18 so I'll keep updating that list as I get more info.
It's just a background for the clan page on the COD app. The clan leader sets the background wallpaper.
You don't get the red clan tag till you reach level 26 my clan is level 25 as of right now I figured I'd inform everyone