Umm, maybe :
Guild search function? (so that players can search and apply etc ^^)
Co-master
Consignment shop/auction hall in guild hall (has pros and cons)
Guild bank/storage (has pros and cons)
Guild announcement board (for offline announcement etc)
More options to sort guild list (maybe by levels?)
Guild vs guild (would be fun)
And maybe increase guild hall capacity (?)
* For the guild search function, can include level requirements, and other requirements as well
Bookmarks