Your kitchen is going to look great. I would go with a white or cream coloured subway tile. Subway tile is timeless and inexpensive and readily available so you should have no problems coming up with some to finish the job quickly.

I would pick several different subways to view in your kitchen. Find some different whites and some cream coloured ones (it is hard to tell from your countertop if there are any cream tone). Also try to find some subway tile with a bit of texture (not a totally flat subway finish) and try one with a bevelled edge to see how you like the look of that.

Once you have decided on a subway tile determine if you want white grout or a dark grey grout (dark grey will add contrast to your space and will feel a bit more modern).

I would skip the accent trim as I think the subway is enough.

Good luck!