It is important to note:
Loshon hora is not limited to speech. Included in this prohibition is communication of the derogatory or harmful information through any means. Therefore, before writing loshon hara or using code, sign or body language (e.g., a cynical smile) that communicates something negative or harmful is forbidden.
To show others a letter or article that would reflect badly on its author is forbidden, as is revealing the identity of the author of a work that is known to be of poor quality. It is also forbidden to show photographs of people which they would find embarrassing.
Sefer Chofetz Chaim, 29 Tishrei, page 106