First of all: Guild Leaderboard
Yeah, I saw this has been suggested a few days ago.. But well why not? No need for banners and all... Just a simple guild leaderboard, to make it easier for us to keep track, especially for guild events.

Which leads to another suggestion: (which I know have been suggested too before)
A guild announcement board, where GM/officers can post upcoming event on there, so everyone can get a heads up and won't miss out on any guild events.

And lastly:
Maybe add a "last seen on ......" for the members of the guild? So we know when was the last time certain players were online. This could also come in handy clearing out the inactive players

Thanks!