Back in my last guild, we had a guild vault set up in order to max out the guild hall.
First of all, you might be asking how will this possibly work.....the success of the guild vault completely relies on donations. It would not be mandatory for you to give money to the guild, but any amount of money would be accepted.
What would happen was that one person (Guild Leader in my last guild) acted as the vault. He would take in all of the donations and take note on the forums how much was donated by someone and the total amount in the vault after each donation. A poll would then be created on the forums to see which NPCs people would like to buy with the money from the vault.
This worked wonders before and we nearly maxed the guild besides 1 50K NPC....
Anyways its just an idea i thought i would share with you all.....
G'Luck,
Kealan