I have seen many homes that had mixed finishes. Mostly white trim and base moulding mixed with stained cabinetry. It looked very nice. I have also seen LOTS of homes that have stained throughout the living areas and white in all bedrooms/baths. This looked really nice as well, and if I had my choice, I probably would have done this on my own home as well. I can't remember any specific posts here, but I have seen many pics of mixed finishes on this site that are lovely. I do have to say IMHO that I would do the crown and base the same whatever you choose. Good luck!

There may be dips in the floor itself and that may be why the bottom of the baseboard does not touch the carpet in some places. Baseboard in rooms where carpet is scheduled is usually installed first and then the carpet is fit up to that...at least that is how it is usually done in my neck of the woods.

You may want to post your question on the Home Decorating forum. I think you'll get a lot more response. The base molding often matches the trim around your doors and windows and crown molding color can vary depending on the wall color. Posting pics of your cabinets and flooring will help. Here is a link that might be useful: Home Decor Forum

I prefer all the trim to match.