The regular perimeter is on the left; to the right above the cooktop is the mixed deco mosaic.

While I adore, no, worship, your deco mosaic, I feel you might be stealing some of its thunder to use it as the full splash in such an insignificant spot.
Is there another spot you could consider?

How about squaring it off like a picture fram with the mosaics and put the field tile in the middle?

Regular with the 4" mosaic. For the 'don't steal the thunder' aspect and b/c it seems you have two outlets there. That would really take away from the beauty of the mosaic.

Regular perimeter backsplash.

I actually really like your field tile too, so again, whatever you do, it's a winner. While I understand that most want you to keep the standard arrangement of the 4" mosaic border, blue pencil, and white field tiles so as not to upstage the cooking area, if you put anything on the counter in that area you won't see the mosaic. I like ellendi's idea of framing the mosaic, so a surround of white field tile, a line of blue pencil, and a fill of the mosaic.

Again, it's all come together so beautifully, you can't miss whatever you choose.

This little piggie says....I don't think you should fill it completely with the deco tile either.

The bear agrees! It would make it too dark and would get lost - you have you one diva - and it is amazing!

Thank you everyone! That's the way I was leaning, but I noticed I was going to have more of the deco left than I thought, so I considered it for a few minutes, then decided the original perimeter would look best. Here's another pic of the perimeter (still not grouted).

That really is fantastic...And the reflection off your black granite is something special!

Gorgeous!!! Great job!!!! Love it!!! Fantastic!!! Also love the reflections!
Any other words?