Market

FE: Increase the size of the item blocks (in /user/extra/market)
Pagination
Search by item name, item group/id, items options etc.
Ability to sell new items. ( where you can pick a character to be shown as a merchant or "hidden" )

BE: When you purchase item it deducts the resources from the user
perhaps even implement a tax% with minimum value (new config) with the ability to turn it off
Cost for selling items in this format: {group:x, id:x, level:x, value:x} | {credits:x} | {zen:x}
(again with the ability to turn it off)