I think Guild system could use expansion. I am going to provide a list of ideas for implementation and i hope that players will comment to improve the ideas.

1.) guild upgrading
a.) increase member count: +5 members for 50,000 crowns per upgrade. no limit. This allows guilds to increase number of people in their guild at a significant cost of crowns. This would be a feature only worth major guilds investing in.
b.) increase available slots members have available to post items for sell in guild store. +1 item limit for 1,000,000 gold per member limit. This means the minimum cost to upgrade item limit is 500m gold to increase limit by 1 and increases if a guild has increased their member count. no limit.
c.) Guild bank limit increase: + 1 guild bank space for 1m gold per upgrade. no limit.
d.) Guild divinity allegiance system: Guilds can dedicate themselves to one of the gods or daedric princes of tamriel. Allegiance provides a boost to xp earned, gold loot from monsters when fighting with guild members by a factor of 25% per guild member stacking up to 250%.
e.) Guild territory: guilds gain access to a territorial zone based on divinity chosen via the allegiance system. Guilds can capture monsters to populate their zones, add harvest nodes, and outfit the zone in a number of manners for guild goals.

2.) guild management
a.) guilds can choose to create a more formal guild ranking system where specific members of one rank(s) are directly assigned to a higher rank individual. (pvp guild focus)
b.) Automatic guild dues system. Guilds can designate an automatic collection of gold each week from each member. Members are asked upon login on the designated guild dues date each week to pay their dues. Failure to pay dues results in automatic removal from guild without prejudice (meaning players can rejoin at a later date). Guilds that do not want dues simply do not set a dues. New members pay dues on the first dues collection date after their date of joining.
c.) players can donate crowns to guild. donated crowns are permanently donated to guild and cannot be a dues requirement. Improvements to guild that cost crowns are drawn from guild owned crowns.