I have remade your Black PM Dr. Mario's CSPs. The reason why it has white lines like that is because of the file having a clear background and it decided to put a color there. Trust me, the file doesn't look like that.
Here is a dropbox of the skins' CSPs: https://www.dropbox.com/s/e7msro9llhnd15r/Dr.%20Mario%20Render%20Pack.zip?dl=0
This was originally made for PM/Brawl, so if you put the portrait in Paint.net and make it a new file, and if you can convert it and add it to your mod, that'd be amazing.