Hello Kumalala-Kumalala,
Generally, when working from reference it is best practice to credit the authors who have inspired you.
When doing "paint overs", I would strongly suggest you contact the authors and get clearance to use their work.
If you are unsure about the license for an image I would be careful about putting it in a finished project.
Maybe a site such as:
https://opengameart.org will help.
https://opengameart.org/content/faq#q-how-to-credit
Unless the work you are using is in the public domain or released under a LICENSE that permits reuse I would be cautious using this approach.
I think this answer should get you started.
Important Note:
I am not an organizer for this gamejam so please double-check with QueenOfSquiggles
Best of luck
Secresteyn