A picture is worth a thousand words.
When you create that facebook ad, check it. If you have too many words on your image Facebook will make your ad more expensive to run. If your cost per… is above $0.20 then it is best to cancel the campaign and find another image with fewer words. Facebook has words available below the picture so add the most important message in the image. “20% off” it’s simple, it’s clean, and it’s to the point.
Here a tool for checking the word density: https://www.facebook.com/ads/tools/text_overlay