Skin Creation, how to make portraits?

Hello everyone. this question is mostly aimed at the Riot skin team and my fellow summoners who make custom skin creations, I have ideas for custom skins and although I cannot 3d model 1 to save my life how would I go about making the portraits for them to give others inspiration to make them (including Riot)? I have seen some very high quality fan made portraits and would like to make some myself, is there any particular program people make these in?