Hmm...

I'm thinking of a bright white subway tile, and I don't know that it would ensure that the yellow tones in your granite don't become too prominent.

I would say that if you are serious about updating it that you start with that little part on the far right. That seems like a good spot to get a feel for things.

I would also switch out the lights to something more modern if you chose to integrate a bright white subway tile. If you'd rather go with another color of tile, I would avoid anything that is cream or that has a yellow undertone.

Have you thought about a light gray subway tile? That might work?

Will you be changing the tile under the 3 cabinets on the left end as well?

Bright white or gray would look terrible with the countertops. Stick with cream or a warm white, the lightest color in the granite.

I think the tile you have ...matches well....but understand your need to do something more interesting above the stove area...since the portrait concept is sort of dated .....how about just adding a column of another tile above the stove ?...this is a fresher approach while still having the same effect as the portrait...

Personally I would get a simple backsplash, nothing different over the cooktop AND I would remove the crown on the top of the cabinets and the arch over the cooktop.

Yes ALL the backsplash is to be changed everywhere you can see that tile will be gone.