This is a grey area. If you download a of a design from 1945, you are generally safe to tattoo that design on a client. These designs have become "folk art"—tribal knowledge shared by the industry for a century.
When you open your , treat it as a textbook. Do not just trace it. Analyze it. Look at how the artist draws a hand holding a dagger. Look at the anatomy of the eagle’s wing. Then, try to redraw it freehand.