Maybe add a system where a certain number of guild members will be randomly picked by the RnG system to do a certain task/quest that they'll do for a week or month which will affect the total guild points/rankings based on their actions to the quests that they've done. (For example 100 members are randomly picked by the RnG system and they are tasked to do a guild quest which will be seen on guild task board; kill a certain amount of this and that etc etc)

I think this will add some competition to the guild rankings. Also I think, a guild badge for top 10 guilds will be an ok thing to add in game too.