Every time you add an update to a Play-by-Play contest, you can update your Featured Thumbnail image. Follow these steps to update your image:

Click Add Update

To edit your entry and add a new thumbnail, click the + Add Update button located top right of your entry page. This action will open up the page builder tools.

Proceed through page Builder Steps

The page builder involves 4 steps to complete in order to add an update.
Step 2 of 4 (Entry Details) is where you can edit your Featured Thumbnail image. Simply click the edit icon and upload your new image!

Complete the remaining few steps and not only will your new update be added, but you will also see your new cover image.