There initially was a comment before mine dated May 26, 2017 which was deleted. It does look silly without it still being there. Many pros look at the date prior to opening a thread. There is a current thread in the pro to pro section on this very topic due to some recent Houzz format changes. By using an old thread you are short changing yourself on available advise. Also due to the rapid advances in technology and products available now many responses given 5 years ago will not be the same as the ones provided to you today. Not to say there is not valuable information in older threads. That's why I bring it up and why you should care. There is your 2017 answer:)

Hello Thrilledtobuild, Building the field tile out should not be under consideration. These issues should be addressed at the time materials are being selected. Unless your installer is giving you a rendered wall (mud job) where he can carve out a channel for the accent, I suggest that you use a decorative relief to isolate the two planes. A simple half-round liner used above and below the accent will define the detail while also obfuscating the 1/8" disparity between tile thicknesses. Best of luck, Shaughnn

How about flipping the tile? Use the grey glossy to line the niche that's in the matte white wall and use the matte white tile to line the niche that's in the grey glossy part of the wall. This may sound odd, but you could use the tiles "as is" or cut them down to mimic the scale of the wall tiles. Example, the grey glossy wall tiles are 4x8. So line the niche with white mattes that are cut down to 2x4, 25% the size of the 4x8s. Same for the other. The white matte wall tiles are 2x8, so line that niche with grey glossy tiles cut down to 1x4, again, 25% the size of the wall tile. Obviously it depends on a lot. Can you cut the tiles. Cut edges. Grout lines, etc. Just an idea. Good luck!

Thanks Riverspots for your suggestion- I have actually seen one repro. of his work (at Ikea they have one which obviously is not the same but by him and the same idea =- women sitting at a bar socializing- but it is this painting- the whole theme of it- that I think is so great! I have researched this up the ying yang (trying to contact a gallery in Israel where the artist currently resides), but to be honest- I can't even come close to paying the prices for the original pieces. This one is (and i say this loosely) only $999.00 Still more than I would ever have spent on art in the past, but reasonable for something of this size and perfection.. I am not so concerned about the colors being off a little- My whole house is .full of earth-tones so I feel like no matter how off they are it will blend. I do appreciate your input though!! If i had a little spare change I might consider buying an original.. maybe someday!!! :)