As we all know, there are a number of NPCs in Classic that will buy different types of loot for double what you'd get from Elster (the guy that buys it all). I think more loot should be sellable to NPCs throughout the map. Example: There should be an NPC that buys jewellery-related loot (gold necklace, gold nugget, all the different pearls). Obviously the railroad shop salesman should buy draisine wheels. The blacksmith should by the disabled nukes. The chapel priest should buy the fake graals. Taylor Richards should buy the boots. Any of the various hat shop owners could buy the zorbi helm. I could go on and on, but you get the idea.
I also think that rare loot should sell for more (and that an NPC other than half-price Elster should buy it). The old gnome in the hidden underground cave shop buys those gems for 150. Why not have him buy the rare "magical" items? Also, the price of said loot should at least be doubled. Currently, no one actually sells the rare loot because it's just not worth it.
Making these changes/additions might help make diving for loot an actual viable way to make money. Also, I think it's about time some new loot is added (including new furniture and/or hats, maybe a rare water pet?).