How to Add Your Own Image as a Panel’s Background

To add your own image file as a panel background:

Click on the Background tab.
Click on the Photo button under the Background tab.

Whether you're starting a new comic or editing one you've already started, you'll need to open the comic maker. Select the Background tab then click on the Photo option. Click the square that says "Drop Photo or Click" to browse for a photo to upload. And click the circle with a line going diagonally through it if you're trying to remove a photo from the background of the slide. This is a great way to achieve the look you're going for if we don't have a certain background that you'd like to use.

To remove, see this article.