That's an interesting style.. What does the rest of your room look like?

By the sounds of it, any neutral colours will work well - cream, beige ect. You could also add a pop of yellow if you're looking to brighten up the space a bit!

Personally I think it is easiest when you choose a palate of colours that work with each other. To make this work choose three neutrals to start with. Given how this house was previously decorated it suggests Mum prefers warmer colours. So say you like Dulux paint you look at their site and choose a soft white such as white cotton and a warm neutral such as Egyptian cotton and then another such as Jurassic Stone. Then I would use these as a starting point and use them again and again in different rooms adding accents. So for instance in the lounge you might paint the woodwork and coving in White cotton, the walls and ceiling in Egyptian Cotton and then a punch of colour in one wall such as the chimney breast. In the hallway you might use White Cotton and Jurassic Stone (in small spaces it is sometimes better to have a simpler palate to make it feel less cluttered and bigger.) In a bedroom you could paint walls and woodwork in White cotton but paint a wall for contrast. Then I would be thinking about what accent colour to continue throughout- So if Mum likes green the living room accent wall could be a bold colour like Heathland, but you might choose a more restful green in the bedroom such as Crushed Aloe, and something fresher for the Kitchen such as Spring meadow. I would use the same neutrals again and again and paint colour with restraint. Then of course you layer on more colour with soft furnishings and you might also give furniture a fresh lease of life by painting it - this trick also helps tie picture frames into a scheme.

I think the main bedroom is wide enough for a headboard wall and room to walk around it. Personally I wonder if the bathrooms are undersized, whether a four bed house with bigger bathrooms would be better, whether you will see a big RSJ cutting across your living room ceiling and if this could be reconsidered. I also think the dining room and kitchen space are undersized and the kitchen footprint seems no bigger than the original which begs the question about where fridges and ovens and storage will fit.