Most Helpful Guy
Typically in the art world, the rule is that there must be at least 3 significant changes.
For instance, if you change the color scheme to make it a blue gradient, that’s one change. If you change the style/texture of it, that’s another change. If you do something interesting with it (like duplicate it in six panels with different color schemes), that’s another change.
Basically recreating the drawing in just a different medium counts as plagarism. That’s why it’s super convenient to take your own pictures and use those as references. This is also why I drew a lot of doggos in high school— I knew a lot of peeps with dogs lol.
If you submit your art to an art competition, they take the paperwork behind it pretty seriously. You have to submit the reference photo, and if they notice it’s not public domain and you don’t make changes, you’re disqualified.
I had a piece of scratchboard art that was geared to win state and was disqualified because some bullcrap about the citations being incorrect with the reference photo. (Granted, it was the administration that goofed up, but then they said “oh well we messed up, but we already awarded places so we can’t regrade.”) The lesson here: citations are important.
Most Helpful Girl
You can't just outright take other people's photos but you could definitely paint this for an exercise. Just as long as you don't say it's yours.
They dont have to be amazing but you could just get friends to pose for you and do sketches where you add things in (eg your friend is running in the picture and in planning sketches you add like, some giant monster in the BG or something then you paint that scene) then paint that.