A good photograph will speak volumes. Carefully chosen, they will accentuate any project. Sometimes though, the adage of a picture speaking a thousand words is overwhelmingly true. There can be so much visual data in an image at times, that the key message may get lost.
For example, trying to describe the canopy layer of a deciduous woodland to primary school kids can be tricky with a photograph. With a simple drawing, the idea is quickly explained. Leaf shapes, too, in a nature project, are better shown with drawings than photos.
Illustrations and drawings can be made to order, and can achieve results that photos simply cannot. Cross-sections, exploded views, cutaways: these are all possible with drawings. A well-executed diagram can clarify a complex idea in a way that an image could never do.
When a project is in its infancy, illustrations as an option and complement to photos should always be on the table.