Would be fun kid hideout space! 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! I love this design.
add wood wallpaper to the kick plates of the stairs. Those rolls are expensive but you would only need one. Not practical with white treads though, it will be stuffed up from black shoe soles in no time.