I would go with something quite plain.

Are you also replacing the shower floor that appears to be faded?

Nope - all of the shower tile stays. It's not faded tile - it's just a lighter version of the wall tile. Trust me, if I had the budget, I'd replace everything. But I just can't stand the badly stained Saltillo, which really doesn't go with that blue tile. And the antique hutch ... ugh.

Something like this white-ish Emser strands porcelain tile in a 12x24 or 6x24 would give a nice clean look and complement a modern sink.
http://www.emser.com/index.php?id1=collectionDetails&productID=422&name=STRANDS(TM)&id0=ceramic_porcelain&index=67&scrollMenuporcelain=476

I would change the tiles in the shower. Having a large walk-in shower is a great selling point and I would emphasize the look of the shower and bring it in line with the cabinet and floor colours.

I agree with going to plain tile. Personally I think a ceramic or porcelain would be better suited for bathroom vs. natural stone.

Is the grout in the shower grey? I would go completely neutral in with a white or grey. And little to no texture, as the shower tiles already have a lot going on. Attached is what I picture, especially when you mention a floating sink. But may be too modern for your home? Either way, suggest keeping it simple.

If you go with white, I would suggest changing the wall paint to match or at least lighten it up to balance out the room. Find some room in the budget to replace the handles in the shower with chrome (or nickel) ones to match the new sink fixtures. And don't forget new fluffy white towels for your showings.

Don't over spend in here though. I'm willing to bet that whomever purchases your home would end up gutting the shower area. So if the shower has to stay for now, then do a simple floor that doesn't draw anymore attention.

I think a pale grey tile, rather than white, could work with this color scheme.
This is not quite like yours (I am sure nothing is) but this might help give you an idea

Kind of what it would like like reglazed with hex tiles.

I like the idea of finding a light neutral grey tile to match with this shower, and painting the walls also a neutral grey that will balance out the shower tile. Sherwin williams has a tool where you import your photo and try on paint colors.....definitely worth a try!

Perhaps you could just wait until you could do the whole thing at the same time. It doesn't make much sense to invest in nice floor tiles (and disrupt your life twice) if in a few short years you'll be replacing the shower as well. I have the same dilemma and I have just decided to wait. (Yes it galls me every morning. But I'm using it as spiritual practice :) I wish you good luck in your search. I love the hex idea somebody suggested above. it looks so nice and it seems forgiving for uneven floors. It has a nice timeless vibe. Isn't it curious what some people (the previous owners) consider "coordinating?" I just shake my head walking around my house sometimes. bonne chance and happy houzzing!

Just give the new owners an allowance for the remodel and let them choose. I would appreciate that so much.

They are selling the house "within the year" so this isn't a matter of waiting to get the bathroom they really want. They need it updated for resale as much as possible within their budget. I'd probably go for a white floor tile with some small blue or green accent tiles in it to coordinate with the shower. I don't think you can go wrong with adding more white to a bathroom for resale, and white and blue are a classic combination.

I agree with others, gray would look nice and tone it down. Paint out the vanity a soft (not a standard BRIGHT) white to freshen it up.
http://www.lowes.com/pd_399387-34692-G8CC15_4294856525__?productId=3799717&Ns=p_product_qty_sales_dollar|1&pl=1&currentURL=%3FNs%3Dp_product_qty_sales_dollar%7C1&facetInfo=

everything redheadedwmn said.

Gotcha. Sorry. My bad. If they're replacing the toilet they could go cool like with a gray toilet and gray tile floor and then paint the vanity. Totally agree. It's a clash of tone right now. The flesh tones of the toilet, floor and vanity just don't look right next to those shower colors. Neither is bad on its own but together -- yeah. Totally. Gray.

Personally, I don't think a gray toilet is the right choice for resale. The issues are different when you are trying to appeal to the widest array of buyers. If you go with whites, then potential buyers don't have to think about redoing anything except the shower eventually. If you go with custom colors for basic fixtures, then anyone who doesn't like the palette has to pull out everything to renovate. It would be different if this were a bathroom the current owners were going to live with for awhile.

Wow - thanks for all the comments. Yes, we're not creating our fantasy bathroom - just freshening it up for resale. I agree that any buyer is likely to rip out the bathroom and replace it with their own style, so keeping our budget low is the way to go. And it's far cheaper to replace the floor tile than replace the shower tile. I think a light gray floor tile could work - and we're definitely repainting (that blue has got to go) and replacing the vanity and mirror. The toilet stays, even if it's a little undersized.

I'll go grab some gray tile samples and see what seems best. I completely agree that keeping it neutral is the best bet. Thanks, everyone!

With 2 different tiles, it seems busy so I would do a plain, decent quality linoleum if I were selling.

My choice is Gray or green Brazilian Slate

I totally agree, go with grey floor tiles, 12 x12", have they laid on the 45 degree angle in order to make the space feel larger. Paint the existing vanity to save money for your new home, paint the walls a softer version of the floor tile. I suspect the new owners will gut the bathroom so don't waste your money decorating for them.