Hi! I am LightofDeath, and using my wild imagination, I was able to get these few ideas:
Homes:
Uhhh....yeah. Buy home sizes, buy decorations from an existing or new vendor. Also a road of homes filled with yours and your friend's homes.
Customizable Guild Halls:
Since every guild is unique in every way, making their guild hall unique too would be a good thing. Like earlier, decors are bought from an existing or new vendor.
New Prestige/Expansion (Whichever you like):
Title: Crimson Knights
Description: Gremlins have captured an innocent Spiral Knight, and has cloned him and his equipment into a fiendish army of evil Knights! Dubbed "Crimson Knights," they are now preparing to invade Haven! Not soon after, Lieutenant Feron is sending a great army of Knights and finish the army, along with it's dreaded leader itself!
Other: You with Spiral Knights vs. Crimson Knights, A.K.A LD-like action.
That's all!
Where was the creativity? Using a different forum name than the one you address yourself with?