15 Additional Flags were added to the game client in 0.7.8.0, as well as one flag getting replaced.
-Basilisk: +75% to XP per battle, +30% to credits per battle.
-Scylla: +50% to XP per battle, +150% to Commander XP per battle, +25% to credits per battle.
-Leviathan: +50% to XP per battle, +100% to Commander XP per battle, +200% to Free XP earned per battle, +20% to credits per battle.
-Pirate Hunter – Tied to an Event for Pirate Day (Sept 19th) (Probably)
-Alaska: Flag for players who have the USS Alaska (Currently on live super-test)
-Le Terrible: Premium Flag for the French T8 Premium Destroyer (Coming Soon™)
-“AL” Flags: Azure Lane Flags, part of the WG/AL cooperative effort, possibly tied to the new Azure Lane camouflages added this patch.
Jolly Roger 6: Commemorative Flag for players Reaching Rank 1 of Ranked Battles for a 10th Time
Purrfurst: The original flag was added in 0.7.3.0, and is now replaced in 0.7.8.0. This flag I am uncertain how is acquired.