Is it possible to create blocks with a plugin?

I suspect the answer to this is a resounding no, but thought I'd ask anyway. Can you create new blocks using a plugin for bukkit? If not can you change the textures on an existing block? Again I'm guessing no, that this is all client side, but thought it best to ask.

I would like to see some more decorative blocks in MC, but if neither of these are possible I might look into the texture packs and see if I can change the texture for an existing but underused block into what I need.

 

I went into a server created by bukkit and they had this weird block that had fire, portal, stone, and gold in one block so i think it can be done.

 

You wouldn't be able to supply your own texture, that's for sure.

 

Not possible I think. Blocks are client side.