Real estate firms may hire photographers or videographers to help market their properties.
Generally, sales of digital photographs are subject to business and occupation (B&O) tax under the Retailing classification, and you must collect sales tax. However, you do not have to collect sales tax if the real estate firm provides a completed Digital Products and Remote Access Software Exemption Certificate.
If you merely sell the right to use your photographs while retaining ownership of those photographs, then you are licensing photographs. In this case, the charges are subject to B&O tax under the Royalties classification, and you do not have to collect sales tax.
The outright sale of all rights to a photograph (e.g., right to copy, publish, etc.) is not subject to B&O tax under the Royalties classification. Instead, this income is subject to B&O tax under Service and Other Activities B&O tax classification.
References
RCW 82.08.0208 Exemptions – Digital codes.
Photography industry guide