I would like to see a new copper ore design inspired by the gorgeous natural copper minerals azurite (deep blue), malachite (banded green), and/or chrysocolla (teal). Since these minerals often occur together, a new design for copper ore could incorporate all three colors and maybe even be attractive enough to use as a decorative building block.
Alternatively, copper ore could have more than one method of processing, where smelting it in a furnace produces copper, while using a stone cutter or crafting table can yield the colorful stones, which could be combined to make decorative blocks with fancier patterns than lapis blocks or emerald blocks and used to make dyes. Malachite would be the best option of the three to make a decorative block since its natural banding would translate best to a Minecraft block that looks good on its own or in a wall.
A third option would be to create a basic copper ore block that's common and a rare malachite variant that's beautiful and is only found in large copper ore veins. If this was the case, they could also add banded iron formations (do a Google image search) as a rare iron ore found in large veins and use the same design as malachite but with a red and black color scheme. Both could be smelted or used as decorative blocks.