Dynamic Product Ads in retargeting do not require you to upload images. Each Product image will be pulled directly from your store's product catalog, which means, you need to make sure the images that Facebook will grab from your catalog are attractive and fit FB guidelines.
Because your ads may be shown in many different placements, it's best if all images and product photos are at least 600 x 600 pixels.
Just like the images you upload in your ads, your product images should not contain any prohibited content according to Facebooks ad Policies, meaning to name a few:
No icons or texts that look like buttons that don't actually work.
No unrealistic "before-and-after" images.
No controversial content that exploits crises or controversial political or social issues for commercial purposes.
No controversial products: Adult Products or Services, Illegal Products or Services, Tobacco and Related Products, Drugs & Drug-Related Products, Weapons, Ammunition, or Explosives, or Unsafe Supplements.
(If you have some products that can not be advertised you can create a product set to exclude these products from your ads. Product sets are a PRO feature)
If your product images are not in a 1x1 ratio (square) you can use Brainity's image crop feature to ensure your products are converted optimally by following these steps.
Enter your Bottom of Funnel dashboard.
Click the upper right-hand button "Product Image Settings"
3. Then choose the crop setting that will show your products in the best light.