Learn English – Different way to say “Courtesy of”

You would dress inconspicuously.

It's best when you've asked the owner of the rights to the material cited (literature, generally) or used (graphics, generally), and that owner has not only given permission but also asked you in return to use that particular phrase to credit the owner.

It's acceptable when you've asked the owner of the rights and the owner has given permission without specifying any particular phrase to use when giving the owner credit.

As requested, this answer omits mention of style guidelines from whatever source (MLA, APA, publishing house, journal, etc.). Where those exist and conflict with the phrasing you've asked about, of course the style guideline would take precedence.