The great thing about Bingo Card Creator is that they're entirely customizable.
Scroll down the page and select the 'Advanced Customization toggle. Next, you'll see that you can add images for various parts of the card, such as the 'Card Background' or 'Card Header.'
Pro-tip: You can blend your background image with a color. Add an image, reduce the image opacity, and change the background color to what you want it to be.
Once you're happy with your card, select create!