10-22-2014, 05:49 PM
The server doesn't handle any artwork, it's a client's job to do so. The server only provides the logic, the behavior of the block. Some custom blocks should be possible to do already, with their behavior defined within the hooks the server provides (such as "if a player right-clicks a block with the custom item in hand, this happens"), some behavior cannot be implemented in the current state (such as "if the block is powered by redstone, make it emit redstone signal of double the strength").