I think you can do a marble vanity and tile for the tub. I even found a photo example. :)

Thanks Emily for sending the picture. I like it. I'm still debating only because mine is a drop in tub with a huge top deck...so there'll be lots of tile. I was always told there needs to be a common thread in design and so far I have wood floors, white cabinet, white carrara marble vanity and subway tile in a separate shower, so there's really no common thread. Thanks.