Look at this for inspiration. Not grand at all, but a sweeping statement of personality and good taste.
Such simplicity, such style, such authenticity, such a successful re-imagining of an old house.
Then right over the top in the bathroom/art gallery! … and why the hell not?
Those colours- yellow ochre, terre cuite, soft green, pale lilac; that elusive and insouciant French style
This shouts “minimal intervention” to me. Deciding what to tweak and what to leave alone is such a necessary skill for a truly successful project anywhere. I think that it takes years to do this properly.