Hello Paul, thanks for the interest in Cultural Japan.
The pictures presented in this site are the properties of museums, from which we aggregate metadata of items and provide search functionalities. Therefore you should ask permission from each museum when necessary. The license/terms of use of an item is displayed on the right hand side of the picture, with a link to the original license page.
Use the "license category" filter on the left side so that you can refine the search results with a license for commercial / non-commercial use. e.g. with
you will find items by 月岡芳年 that can be used for commercial purposes.
Hope this helps.
cheers,