When viewing a simulation from the dashboard, your learners will see a thumbnail associated with each simulation.
By default, the thumbnail will be whatever media is first in a sim - usually the cover/title page. You can change this to a custom image using the following steps:
Head into the Sim editor
Click Properties
Scroll down to "Placeholder Image" (Thumbnail Image)
Uploading a square image file is optimal, as the end result is circular. Avoid using small text as it will be hard to read from the learners perspective. For example:
Click save!
Your learners will now see the updated thumbnail image on their dashboard: