Few random thoughts

Saccing certain items with stats could randomly give you the choice of taking
a blessing that lasts 1 boot (or certain game time), and gives bonus based
upon the stats of the sacrificed items, or instead of items you could
sacrifice corpse and there would be bonus to skills or spells based on your
guilds and random factor.

Event like Shinarae did. This would run every so often. It would not be pvp,
nor guild vs guild. Instead every background would have their own type of
event that would require most of the guilds into a party that would do certain
tasks together that would change between events. For example civilized would
require bard, merchant, alchemist to create certain flask and mine certain
minerals, then finally sabres, or knights would come in and help them to kill
a few monsters to finish the task. Completion price would be small background
oriented bonus +few skills,regen or something and item or two for the

party/parties that finishs the event.