Sample Ad is an advertisement that is created to demonstrate how a product or service would look in an actual marketing campaign. Sample Ads are usually created to show potential customers the features, benefits, and overall look and feel of the product or service being advertised. They are often used to test out different ad copy and creative styles before committing to a full-scale campaign.
You are able to do this in 2 ways:
1. Enable sample ad here: Ads Pro > Settings > Media > Example Ad if empty Ad Space > Yes
Here you can change content of sample ad: Ads Pro > Translations > Sample
And change custom sample image via shortcode parameter (optionaly): [bsa_pro_ad_space id=1 custom_image=IMAGE_URL]
2. Display other ad space if the main space is empty: [bsa_pro_ad_space id=1 if_empty=2]