The same thing happened to us but on a bathroom floor. Our tile guy came up with a brilliant sollution and made a "rug" out of other tiles that were complimentary colors. The whole thing looked very Frank Lloyd Wright...it worked out well. I would get some glass tiles and put them on the 12 tiles at the corner...I have seen some great ones out there. I fell in love with some circular glass tiles that are available at Home Depot...you could make it look deliberate and place the glass tiles at different places on the tub. For the cheapest quickest fix-a plant or basket with towels...hope that helps and please post a pic when you're done.

Perhaps have the bottom two rows of tile dug out by a tile contractor and retiled in a solid matte black or grey. The tub surround will then be rimmed at the top by the existing tile.
That way you don't have to retile everything. Alternatively pull off all the tile just on the tub and retile with something that harmonizes.

One more thought-if it's possible to move the tiles you could take a tile from another place on the tub and move it around...you could also take off some, smash them and then put them back intregrated with smashed mirror and glass tiles.

Think about filing an insurance claim... you might be able to get your whole bathroom re-tiled if there is a matching issues, accessing the leak is a covered loss.

Why not retile just the tub surround?

I agree with bepsf. retile the tub surround - you can perhaps get white tile as the right wall in the photo, or ceramic penny tile in a dark grey with white grout.

I fear if you start piecing the tiles or getting too crafty, it will start looking wonky.

Retile the facing of the tub with a checkerboard pattern - find a complementary white tile (same size/style) and do every other. That will free up some of the darker tiles to cover the broken area.

It should be a quick and cheap repair if you limit the repairs to those two surfaces, especially since much of the area is cut tile (so you can use either end of a single tile instead of buying two).

I think that the above idea of retiling the bath surround with the white tiles that are above the bath would make for the best result. However, if you want to personalize it (at the risk of the resale value, you could tile the corner - both the damaged and undamaged sides - with coloured glass tiles.
I also found some adorable accent tiles on Etsy
http://www.etsy.com/listing/36524919/beaver-plumber-art-tile-coaster?ref=sr_gallery_5&ga_ref=auto&ga_search_query=ceramic+tiles&ga_search_type=handmade&ga_facet=handmade

... but I don't think that it would be a very good idea to put something so awesome/personal into the bath area. But if you do want to go for an accent tile that looks like something in particular, I'm sure that one of the clever artists on Etsy could make something the right size for you!

Good luck!

What strikes me is that the plumber had to make himself a whole to create an access to the siphon (or whatever concerned by the leak...).

I'd simply suggest you to nicely finish the thing and create a real access to the water system of the bath tube with a hatch...

Next time an issue happens, the guy will just need to open the door of this hatch.

You could paint it white to match your bathroom color scheme or whatever color that fits your tastes.

Would this be a way to explore?

Cyrille has a point about being proactive. I nabbed a bag of bathroom tile floating in the storage room of my condo building just in case this kind of thing happened to me. I don't know who left it there but it matches my bathroom and it's mine now! I also noticed I have no access to my bathtub plumbing and would have to break thru a wall. All my older apartments had access thru a closet or some little door somewhere. I don't know why newer construction doesn't do this anymore but I'm thinking it's a mistake. Unfortunately nothing lasts forever.

Ditto the access hatch idea - if finished out nicely, it would look fine. Plus, having a way to get at your plumbing comes in very handy.

Aren't tubs like that required to have access panels? We've always had them for tiled bathtubs.

Replace the broken tiles with bright pink tiles. Or get inspired by Invader.

Square up the opening and build a flush mounted access door from the same wood as your vanity. You may need access to the pluming again. Very Scandinavian.

Just a heads up - if you are planning on only replacing a small amount, remember that most tile shops sell tiles by the full carton (anywhere from 5-15 square feet). While this usually would give you a few extra to tuck away, it would give you way too many in this case - wasting money and storage space! Retiling with a neutral, even-toned tile and adding an access panel (some can use velcro, hinges, or just screws) would add value to your abode!

How about installing an utility door for future repairs.

I would (very carefully) remove some tiles from the end of the tub and use them to replace the broken tiles. Then I'd place an access panel on the end of the tub--I'd use something like a nice, sleek piece of brushed stainless steel held in place with hidden compression fittings.

(Your plumber was a dipshit hack. Instead of attempting to carefully cut through the grout lines and remove only as much as necessary to get access, he indiscriminately whacked a hole though with a hammer?)