Enjoying the hot springs (Onsen) is definitely a recommendation, but how about some indoor activities such as visiting the trapoline park, experiencing Japanese culture with workshops, shopping at the famous outdoor brand stores (Snow Peak, Northface, Patagonia, and etc.), and enjoying a relaxing time in lovely cafes and restaurants?
For details, please refer to these pages.
・Onsen
・Shopping
・Hakuba Japanses Workshops
・Other activities
・Restaurants and cafes

Also besides skiing and snowboarding, Hakuba offers many other winter activities such as snowshoeing and snowmobile tours. Exploring other outdoor activities could be your option too!