I imagine you won't be changing the layout. I'd be measuring everything and shopping for my elements (tub, toilet, flooring, vanity, lighting, plumbing....) What type of storage do you need? Do you prefer a cabinet type vanity or one with drawers? Is an extra cabinet above the toilet necessary or can you find a vanity that will stock everything? Perhaps a medicine cabinet would make sense? Could you do a recessed one?

My suggestions: keep the design simple and easy to clean. I like slab or shaker doors on cabinets - nothing with a lot of trim or details. I'd keep everything white (perhaps a wood tone vanity) and add colour with a fun shower curtain that can be changed every few years, bright towels, soap dispenser, etc. The essential thing in a bathroom is that it be done well so I'd skimp on the lighting fixture before the labour and waterproofing.