You (as the contributor) do! You retain the copyright (ownership) to all the images you create and own. In exchange for the fees paid to you for your accepted content, you grant Unsplash a non-exclusive, perpetual license to display and market your images on the Unsplash+ website, and the further right to license your images to Unsplash+ subscribers.

Full details about your, and Unsplash’s, responsibilities will be outlined in your contributor agreement once your contributor application is accepted.