Images can be added to each Course for use in Tile layout or for thumbnail images in Classic layout. They can be uploaded by going into the Settings sub-tab of the course and selecting "Choose File" in the Course Image section.

Proper Course Image Sizing

• If you decide to use square course images, a square 1x1 ratio like 450px x 450px would work perfectly, you can scale up for higher resolution, say 1000px x 1000px.
• For rectangle images, you can work off of this pixel ratio: 450px x 253px (or multiples of for higher resolution, i.e. 2X -> 900px x 506px, 3X -> 1350px x 759px).

Note:  Tiles are only available on the learner side.  See this article to change your theme.

Note:  Square tiles in view are 250px x 250px and will be stretched to fit the tile.  Images smaller than 250px x 250px will be stretched. 

We covered this and more in Litmos Dojo. Check out the course How To: Build a Course - The First Step.