@nilfanif: Any type of graphics

Any type of graphics submissions is acceptable only if it was explicitly requested by the project owner or if the contributor can provide a clear proof that their submission has been accepted and used in the project.
Project owner indeed said that your work is scheduled for 0.15 series, but still, there is no guarantee your work will be use in the project. The project owner could easily change his mind if any other good design come in.
I suggest you to submit your work to utopian only after the PO merged/used your work.
Submissions must include credits to all third-party images/assets used in the contribution. It is up to the contributor to ensure they have permission to use these assets (images, videos, fonts, 3D models etc.) for commercial use.