Rearrange your text until it is readable again. This is a little bit better.
Not a banner I'd choose to have on my page, but it shows what you can do with a background image.
To save this slide as a JPEG, pull down the File menu again. Choose "Download As," and then JPEG. The whole slide is now saved as a file image, which you can use however you want.
Simpler is better, don't you think? I like the solid color background better than the busy image.
I use this method to create graphics that are really versatile. Today, I made collage images with a title for my three top blog posts using the post photos, the title, and my website name. I added links, and then put them on all my pages as sidebar widgets. I think they're really eye-catching. They're Pinnable, too!
If you want to make a series of images with the same format, you simply duplicate that slide and replace with the new images and text. As long as you have the new slide selected, when you "Download As" a JPEG it will only save that current slide and not the entire presentation, just like the first image you saved.
I hope you enjoy using Google Slides to design some graphics for your own site!
--Kelley