Ok, here goes! Over the months, I've had quite a few ideas for prefixes. I've sorted them by type and think they're pretty cool! It could work as some sort of achievements thing, too.
Beginner
[First Egg]- Break an egg in EggWars.
[Looter]- Open 20 chests in Skywars.
[He's getting away!] Steal a flag in BlockWars.
[Unlucky] Die from a Lucky Block in Lucky Blocks.
[Got Potential] Kill 10 players in Battle Arena.
[50-50] Enter overtime in BlockWars.
[I Am The Eggman] Break 2 eggs in one round in EggWars.
[Wah] Win a round of Minerware.
Intermediate
[Addicted] Play for 24 hours.
[Chicken] Bridge 500 blocks in EggWars.
[Death from Above] Snipe somebody with an arrow, and kill them.
[Eggwars 2: The Revenge of the Player] Avoid falling into the void with an Ender Pearl in EggWars.
[Social] Have 5 or more friends.
[Pit Fighter] Enter the pit 50 or more times in BlockWars.
[Cuberaft] Enter water for 10 seconds or more in Pillars of Fortune.
[Intentional Game Design] Break 5 beds in BedWars.
[We Built This City] Place a tower in EggWars.
[Critical Hit] Take no damage and win a duel.
[That Time Of The Year] Play a seasonal game.
Advanced
[KB] Use a brush on suspicious sand in Pillars of Fortune.
[Insert Prefix Here] Get on a leaderboard.
[Mr. Eggwars] Get over 150 wins in Eggwars.
[Unstoppable] Get a kill streak of 100 in Battle Arena.
[Sky Police] Elminate 500 players in Skywars.
[Godly] Ride a pig in Pillars of Fortune.
[prefiks] Unlock all other achievements.
Beginner
[First Egg]- Break an egg in EggWars.
[Looter]- Open 20 chests in Skywars.
[He's getting away!] Steal a flag in BlockWars.
[Unlucky] Die from a Lucky Block in Lucky Blocks.
[Got Potential] Kill 10 players in Battle Arena.
[50-50] Enter overtime in BlockWars.
[I Am The Eggman] Break 2 eggs in one round in EggWars.
[Wah] Win a round of Minerware.
Intermediate
[Addicted] Play for 24 hours.
[Chicken] Bridge 500 blocks in EggWars.
[Death from Above] Snipe somebody with an arrow, and kill them.
[Eggwars 2: The Revenge of the Player] Avoid falling into the void with an Ender Pearl in EggWars.
[Social] Have 5 or more friends.
[Pit Fighter] Enter the pit 50 or more times in BlockWars.
[Cuberaft] Enter water for 10 seconds or more in Pillars of Fortune.
[Intentional Game Design] Break 5 beds in BedWars.
[We Built This City] Place a tower in EggWars.
[Critical Hit] Take no damage and win a duel.
[That Time Of The Year] Play a seasonal game.
Advanced
[KB] Use a brush on suspicious sand in Pillars of Fortune.
[Insert Prefix Here] Get on a leaderboard.
[Mr. Eggwars] Get over 150 wins in Eggwars.
[Unstoppable] Get a kill streak of 100 in Battle Arena.
[Sky Police] Elminate 500 players in Skywars.
[Godly] Ride a pig in Pillars of Fortune.
[prefiks] Unlock all other achievements.