Why do you not want any grout lines? You could put them close together but even if you do I believe you would need to grout maybe with unsanded grout to fill in any little openings... you definitely do not want moisture to get in behind your tiles. If you do put them right to the wall you will need to prep the wall. Score it really good so the adhesive will grab. And, use thinset so they will adhere. You can't go wrong with thinset.

I wish I could help. I have been thinking about glass as our backsplash as well, but I had seen examples like yours that have scared me away from it. Not sure if it is an installation thing or just common with glass tiles. Hopefully it is something that is easily remedied however!

If you don't grout, something will fill those miniscule crevises, especially in a kitchen (unless this is entirely in a non-work area, perhaps?). Splash something up there while cooking and that lovely red sauce seeps between your tiles and is now a permanent stain BEHIND your beautiful glass tile. Eeeew.

I spoke to someone at South Cypress Tile and they told me what mortor to use and gave me two choices for grout. One choice was Bostik diamond grout. She said since we are going with a white glass subway tile (it has a very slight grayish/blue under tone) that the diamond grout would really make the glass tile pop. She also said it's more stain resistant. But she did warn me it costs much more verses the other grout she recommended. Have any if you guys used this grout? Was it worth the extra cost? Does It hold up well long term?