On interior design I've always found the French to be very good here, so would suggest you have a look at the specs for, for example Citroen C8, C4 Picasso, Renault Espace & Scenic etc.
Note these are all people carriers and therefore aimed at families with kids.
Some of the little touches I've experienced or heard about which could make the interior better:
Drop down / fold away mirror to keep an eye on the kids (or be used by your IAM observer!) - fitted to the C8 but placed too high to be really useful
.
Low level all round lighting - fitted to the C4 Picasso
Variable panel light brightness - fitted to many cars, the best I found was the simplest which dimmed the panel lights automatically when the headlights were turned on.
Loads of storage space for both big and small items. Loose articles are distracting if you can hear/feel them moving around.
Chunky controls are better than small, fiddly ones - radio and aircon designers take note! My wife has always liked those found in the old(er) Skodas such as the Favorit. Also I find flush buttons more distracting than ones that stand proud since you can find them with your fingers, not your eyes.
The speedo should always be directly in front of the driver's eyes - C8 designer take note
Please, please design me a carpet that doesn't trap every particle of dirt, mud, crumbs, chewing gum etc. with such a tenacious grip you need a Sellafield powered vacuum to clean it
No control should be a stretch for the driver's arm nor any readout a stretch for the eyes - tiring and distracting.
And finally, perhaps link a control to the clock so that say, between 8pm and 6am, a regular (say every 20 mins), intrusive beep occurs that the driver has to cancel - the C8 seat belt alarm seems suitably annoying (but not distracting).