For the short term, I'd repaint, get a new mirror, and put a large shelf on that open wall for towel and toiletry storage (like one of those ikea expedit cube shelves). In the long term, I'd replace that shower with a gorgeously tiled huge walk-in shower and add a large vanity instead of that itty bitty pedestal sink. Pricing will vary depending on where you live and how expensive your tastes are, but you're looking at prob $20-30k to start.

I'd start with the question of function? If it were my master bath, I'd be looking for towel/TP storage (closed cabinet on wall across from shower) a make up table (big wall) and towel rack (next to shower)

Definitely add a larger vanity for storage, and paint. Down the road think about adding either a tub/shower combo, or a large walk-in shower all along that wall.

New mirror- a framed one. And you can add a pretty wall armoire or open shelving unit to roll towels. And paint- alabaster to brighten it up. Above toilet and on wall in front of shower maybe some art work.

Thinking and looking some more:

Short term/low cost: new vanity, toilet, towel bars, paint: $3,500

Long term/high cost: gut job and redo. $20,000.

Here are some vanity ideas from Lowes and colour suggestions. BM "maritime white". These should go well with your tile. Eventually add a larger shower.

Wow! So much wasted space. I would make a bigger shower like others have suggested but I would also switch the sink to the adjacent wall, which it looks like could handle a much longer vanity. Of course that would mean new plumbing, so just swapping the pedestal for a vanity that reaches the wall would be fine.