When I taught a computer repair class for high school students there were two ways that I consistently used pictures and diagrams in formative assessment.
Formative Assessment With Images on Formative
Every week I would have students answer questions based on a diagram that I upload to Formative.com. I like using Formative.com for this purpose because I can add multiple questions to the same diagram. Students know exactly which part of the diagram each question is referring to because the questions appears when they click the diagram.
Students Documenting Processes With Pictures
One of the first hands-on activities that my students would do every semester was to disassemble and then reassemble some old desktop computers. Originally, I was going to have students draw diagrams throughout the disassembly process. That proved to be time-consuming and inaccurate (sloppy drawings, poor penmanship). So I switched it up and had them start taking pictures on their phones then labeling those images before sharing them with me via Google Classroom.
The act of photographing and labeling wasn’t graded (other than done/ not done). I wanted to see which students could recall and document well and which still needed help with the process.