Thank you for reaching out to the Community about your Event Campaign. We'd be happy to help you delete this place holder image. If your logo is already inserted, this place holder image can be removed by selecting and highlighting it, then hitting the delete button on your keyboard. Please let us know if this helps!
For any future events, we would suggest right-clicking on this place holder image and selecting "Insert/edit image" in the drop-down. Doing this will allow you to replace this section with your own logo.