I love the idea of a separation wall with an inbuilt fire which creates a feeling of warmth throughout especially against the light, soft grey paint. It adds in a subtle way element fire to the white-grey (metal element) interior.
Awesome dog kennel under the stairs design idea. If you want an indoor dog house, utilizing the space under the stairs for a cozy, attractive and practical space for dogs is a good idea! The barn door really ties it together.