To allow stakeholders to quickly understand which launcher to choose for their specific design, having a thumbnail inside, to the left or right of the launcher box will provide a visual representation, especially for those new users.
The problem is that the "preview" option in already created campaigns takes quite a bit to see what a template looks like finally. Previewing a launcher is quite different as it only displays what fields/tokens are in the launcher, which is not what an end-user expects to see. This thumbnail would speed up launcher selection, create a better U/X, and increase platform utilization.
To simplify end user use of this thumbnail assignment. Maybe the launcher can have an option to choose a campaign that has used the launcher template and can autogenerate the appropriate thumbnail size. If too small, clicking or hovering over the thumbnail can display a slightly larger thumbnail. This feature would eliminate any client-side requirement to generate thumbnails for the launcher, only creating more work on the client side and possible hand-holding on the vendor side.