A source register connects each downloaded image to its origin and intended use. It prevents a folder of attractive references from becoming a collection with no reliable context.
Record the basic facts
Store the video URL, video identifier, download date, selected dimensions, and local filename. Add a short note explaining why you saved it, such as studying a comparison layout or archiving your own published cover.
Separate observation from permission
The fact that an image is publicly accessible does not establish permission for every reuse. Keep permission or licence information in a separate field when relevant. Do not fill missing information with assumptions.
Maintain the connection
When you rename or move a file, update the register. Keep edited derivatives linked to the original source record. Before sharing a research folder, review whether each included image is appropriate for that handoff. A small accurate register is more useful than a large archive whose origins can no longer be reconstructed.