1) Is it necessary to have two sets of category icons along the top of the screen, one for the PC and one for the NPC/container? I feel like more times than not, that would just lead to extra clicks, to keep the two lists in sync. It might free up a bit of real estate (for an NPC or container name, perhaps) if there was just one set of category icons, that controlled both lists. (Or if you do have two, could there be a "keep in sync" checkbox?)
2) I do think it would be useful to include the 3D item display, because items like "Fine Clothes" and "Boots" come in multiple versions with different appearances, but all have the same name. Without the 3D display, there would be no way to know which of these you were buying or selling.