Bumping because jRO just implemented a reward system for utilising SecureOTP Mobile to generate secondary passwords for use on their launcher page (jRO's login system is web-based and integrated with the game's online homepage), and while not precisely the same thing as a loyalty event it showcases the kinds of rewards one can offer to incentivise and facilitate play.
For logging in with this additional layer of security, the player will be cleared to receive a special coin item from an NPC. These coins have no intrinsic value and can be redeemed periodically, once per week (our system would be once per day since rewards of this caliber by week are retarded). By then presenting these coins to another NPC (located in each town), the player can trade them in various ticket items called proofs, and depending on the number of coins traded, from 1 to 4, the player will receive a heap of bonuses for up to 180 minutes. Each "grade" of proof gives you new bonuses in addition to ALL of the bonuses that a lesser proof would have provided, e.g. Silver gives you both Bronze and Silver buffs, Gold gives you Bronze, Silver and Gold buffs, and Rainbow gives you absolutely everything.
Bronze Proof - 1 Coin: +5% EXP gain from killing monsters.
Silver Proof - 2 Coins: ASPD potion effect, elemental endow of your choice (180min duration!) for 30k zeny or the corresponding elemental converter, universal town warper access for 5k zeny per use.
Gold Proof - 3 Coins: AGI Up movement effect, HIT/FLEE +10, complete HP/SP recovery for 2.5k zeny.
Rainbow Proof - 4 Coins: MHP/MSP +20%, universal dungeon warper access for 10k zeny per use, gear repair along with the Gold HP/SP recovery bonus effect.
Notes: All bonuses except the +5% EXP gain will be lost on death, ASPD potion effect is based on the most powerful ASPD pot for your class, AGI Up effect and MHP/MSP +20% effects are lost on Siege maps incl. TE, warps to areas barred by access quests will be unavailable unless you've completed those quests.
We need to implement something like this for our loyalty rewards.