You can use OnSong to create custom chord diagrams that can be utilized for your chord charts. Learn how to create custom chord diagrams using these resources:
Tutorial video discussing chords and chord diagrams in OnSong: http://onsongapp.com/videos/chords
Page from our user manual about the Chord Diagram Library: http://onsongapp.com/docs/interface/menubar/utilities-menu/editors/chord-diagram-library/
Page from our user manual about creating chord diagrams from within the Chord Diagram Library: http://onsongapp.com/docs/interface/menubar/utilities-menu/editors/chord-diagram-library/create/