Ever wanted to show a fancy squad patch on your vehicle or gear at all times? Want to represent a group without changing your profile name constantly? This is what the Squad.xml is for.
Where once this was complicated, it has been made simple by the awesome Arma community with hosters like https://armasquads.com/.
This will take you 5 minutes. Don't get scared, this is dumbshit easy.
Visit https://armasquads.com/ and register an account
Go to menu -> squads
Create a squad. The TAG is what shows up at the end of your name. Ex, "Kalthramis[AI]"
Upload an image. It must be any multiple of 16, ex 16x16 or 32x32. For the best quality, just use the largest size; 256x256.
Return to the squad page, and click "members" -> "add new members"
Go into Arma's main menu, config, profile. Copy your playerID.
Paste this ID into the correct line for "add new members." Fill out the rest of the information as you see fit.
When you are finished, return to the squad page, copy the large URL for the squad.
Return to Arma's profile in-game. Paste the large url into the appropriate line.
Ta da! Any online server will now utilize your squad TAG and image. Be aware that everyone can see this, so if you use something appropriate, it could get you banned from the server - or worse, BattleEye banned if you are reported to Bohemia.
Have fun!