I would do a white bathroom with porcelain tile, keeping it very simple. If you're in a cold climate, I would consider a heated flooring system.

Since there looks like enough space, I'd do a double vanity.

I hope you're able to do it for $10,000-I assume that includes contingency, which is a bit worrisome since there always seems to be a nasty, expensive surprise when it comes to redoing a bathroom.

The bathroom picture below shows painted wainscoting on the walls, which is something you can do yourself and is a cheaper alternative to tile. Notice that the shower/tub combo tile surround doesn't go all the way to the ceiling, which will cut some costs as well.

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I don't see why you couldn't do some sort of built-in where the storage cube is, like they did in the picture below. A shelving system installed between the studs would look nice there, and if you wanted it hidden I'm sure some doors could be added. Or, if you're handy you could build it yourself; drywall the space after the tile is gone, then install shelves between the studs.

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Will you have enough clearance between the commode and the tub if you increase the tub/shower size? I'm not sure if there are codes that dictate a certain amount of space around a commode, so I'd double check.

Lastly, have you considered a grab-bar in the shower? The reason I ask is because I had knee surgery earlier this year, and I really, really wished I had one in my own shower :)

Good luck with your reno!