Currently, server shops only accept Lapis Lazuli. I originally discovered that I was mining all of my ores with a silk touch pickaxe and then selling all of them; however, I would have to empty my inventory and then place and mine any Lapis Lazuli ore I had picked up while mining. Adding Lapis Ore to the shop would be a convenience to miners. Juran also pointed out that Lapis could be priced so that it could be sold as regular Lapis or the ore, except someone with a high fortune pickaxe would be able to obtain more lapis per ore and sell the obtained lapis for more on average than if the player were to mine it with silk. This way, players can sell it as an ore or as regular lapis for their convenience, but also provide an advantage to those who have acquired higher tier pickaxes.
For some reason I can't click to add a poll, I can only highlight it. So please in the comments below if you could add a +1 or a -1 for your decision to add Lapis Ore to the server shop. Thanks!