Buzz: Tips & Tricks

This might be what you are looking for:

Select Settings in the toolbar:

• Define the Title and Term in the Course section of the General tab.
• Upload a course image and/or choose the color in the Thumbnail tab.
  • Recommended thumbnail file type: PNG or JPG (Buzz converts all files into PNGs)
  • Ideal thumbnail size: 400px x 400px (Buzz automatically resizes images, so uploading images smaller than 400px x 400px may reduce quality)

From here:  https://support.agilix.com/hc/en-us/articles/208050653-How-do-I-manage-Course-Cards-