Promised! More suggestions by YOU will be added in the may update.
To be precise: There will be 4 more challenges: Increase your level (beginners only), win x prestige (x depends on your level), reach x morale (only if you have low team morale) and win x matches with a specific formation (platinum challenge, so teams below level 30 will get it rarely).
Stay tuned for more infos about the update each day this week!