Add {{disputed diagram|why}} to the top of the disputed diagram, replacing "why" with your reason. To specify the talk page section for discussion other than “Disputed” (default), use {{disputed diagram|why|talk page section name}}.
{{References missing}} – generally for files where the description or depiction needs references
{{Datasource missing}} – for own diagrams and maps visualizing data that needs references
{{No source since}} – deletion warning for missing essential source information
{{Sourcefield}} - produces a warning that a file appears to have an invalid entry in its "Source" parameter; for use on user talk pages, not file pages; less serious than the {{No source since}} warning; does not threaten deletion