Here are my favorite websites for finding images to illustrate your family tree.
National Archives Photo collection
The National Archives in The Hague has over 14 million photos in its collection, many from press offices, taken by professional photographers. Over a million photos have been scanned and made available in the photo collection at the Nationaal Archief website.
Cultural Heritage Service
The Rijksdienst voor het Cultureel Erfgoed [Cultural Heritage Service] oversees the preservation of monuments. Their online photo collection includes photos of many buildings, including churches and houses. Most photos show the exterior but there are also photos of interiors of some buildings.
The website is available in Dutch only, but you can simply search for the name of the town where your ancestors lived.
The photos up to 1200×1200 pixels are available under the Creative-Commons-Attribution-ShareAlike (CC-BY-SA) license.
The Rijksmuseum has been digitizing their collection, and made the images available as public domain. This means you can use them any way you like.
Picturing the past
The website Picturing the Past presents images from various sources, including prints of occupations and ships. They are all in the public domain so you can do what you want with them.
National Archives Map Collection
I love maps, and the National Archives in The Hague has the largest map collection in the country, containing more than 300,000 maps. Better yet, many of their maps are manuscripts, one-of-a-kind documents. Thousands of these maps have already been scanned, and are available as Public Domain images on the Nationaal Archief website, to use however you like.
Many archives provide online access to their photo collections. In a search engine like Google, search for the word “Beeldbank” [image bank] combined with the name of a town to see if there are any online image banks for the town where your ancestors lived.
The Image banks section on the Digital Resources website has links to several regional and local image collections. Beware that images may be protected by copyright.