First i would say -
Make some events with some Rings and the end - For the easy event
Next a event with a neck at the end - For the hard event
Then i would say make Some New gear the a world pve boss drops, Say LK With 700k hp and a 5 man run, He would drop some new gear bit by bit, Say respawn of about 10mins - The gear wouldnt be to overpowered just like an upgraded s8 (Nickname of s9) Ofc it would be in the sets - Paladin holy, ret, prot - Druid, Dps, healing, tank.
Next for donors i would say make it so they could use some commands say - Morph, Appear, Summon, Revive.
For voters i would say some Weapon upgrades - Shadowmourne v2 from 1.5k Damage to 2.3k Ect Different weapons for different specs i.e Healer - Dps - Tank