Add a Project Image
To help distinguish projects you manage on Tableau Online (and help your users find them), you can add an image that appears in the thumbnail.
Set a project image
Sign in to a site on Tableau Online. In the list of Top-level Projects you have access to, select or navigate to the project you want to update.
If you're not sure where to find a child project, use the Explore drop-down list and select All Projects.
Click the Details icon (i), to open the Project details dialog box, and then click Edit.
In the About field, at the end of the project description, add the URL for your image using the following syntax:
Select Show formatting hints to see how you can format description text.
Note: Images embedded in project descriptions cannot be resized or positioned. Recommended size is (300 x 184 pixels). In addition, they must be added at the end of the project description and be enclosed in ! (exclamation marks), otherwise they will not be displayed as the thumbnail.