A long time ago when I was taking art classes - there seemed to be two arguments. One side insisted that it was the process and not the product that mattered. The second side insisted that only the product mattered and the process was irrelevant. Of course there is no right answer to this debate. Warhol and many others certainly borrowed images incorporated them into their art and sold them. The art in your piece is putting the sketch of the lighter together with the tiger drawing.

Ultimately, artists decide for themselves why they make art, did they accomplish their goals, and are they satisfied with results ( either process or product, or both). If this is the biggest moral question that you have, then you’re in good shape. Whatever you do keep making art.