You really did tick the most essential options on the C-class!

Even the color is great, Tenorite Grey is one of the best colors available on a C-class in my opinion.
I don't know how tall you and your folks are but having Panoramic roof would decrease the front headroom. So if you're tall, you'd be better off with just a sunroof.
By the way, are you getting the 17" or 18" AMG wheels? You posted that it's the 17" AMG wheels but the picture in your post shows the 18" AMG wheels.
Anyway the Black/Beige interior is really nice but as with all light interiors, it does get dirty very quickly if it isn't going to be taken care off every once now and then.
In combination with lighter interiors, I prefer wood inlays over aluminum because it looks too cold and clinical otherwise in my humble opinion.
The Cognac Brown interior seems to be less vulnerable against light smudges.
My personal favorite.
The Dark Grey/Grey interior is great as well. I believe they made the upper part of the dashboard and the upper doortrim dark grey because otherwise the contrast would be too great if it was black combined with the lower part of the dash which is of a lighter grey color. I think it looks great as well, the only interior color which isn't 80% black that you were refering to earlier.

I have saved a few photos of the a Tenorite Grey C-class with Dark Grey/Grey interior a while ago because it was such stunning combination. It was on sale a few months ago and obviously sold already.
Aside of that there're a few small options that are in my opion worth considering:
Park distance control
Very useful in tight parking spaces and reversing especially if one don't know how far the boot or hood stretches. And sometimes you could hit something you can't visually see like a small pole, trailer hitch or a small kid playing.
Heated / Cooling seats
Nice for the winters and summers especially if it's leather.
Full electric seats
The full electric has memory function for like 3 persons.
Worth considering if the car will have multiple drivers with great length differences and driving positions (laid back or active).
Automatic trunk closer
Not really necessary but a nice addition if you don't want to get your hands dirty.
Black headliner/roof
Not really necessary but it does add some richness to the interior in my opinion.