Please keep the original features.

If you like modern then you can use fresh colours and patterns for your furnishings.

Why not best of both ? Keep the architectural elements ( trim, doorways, structural etc) as cottage but furnish with modern/simple lines. You could balance this well and use the simple modern elements to accent the vintage. I did this at a beach cottage and worked out very nicely. You'll find at times vintage on vintage can drowned out the architectural beauty of things like your doorway. Good luck !

If everything is painted a not too cold white including all trims and ceiling, then you can do whatever you want. ECLECTIC is fabulous because it allows you to collect and express yourself. Remember that hanging wall things , needs to be at eye level...expands the room and prevent the 'passage look".