Guild houses should be 0% with a guild only save term so you can train in PvP.. also startup style shops could be purchased.. along with insurance reclaims and bank terms
Guilds should be able to create flags and some kind of shortend version of their name.. so a guild house can bear the guild flag/logo. And members (if they choose) can have the shortened version of their guild appended to their name e.g.
[Sntnls] Susanooh
(thats me.. im a member of Sentinels)
Also if you want you should be able to show ur rank e.g.
[Sntnls] Susanooh [Sqd Cmd]