• Placing the most important content at the center 50% of the image asset
• Using images with a white background since these images usually deliver better results
• Providing square images exclusively in order to maximize how often assets are able to serve.
• Making it a habit to upload four or more relevant and unique images at the campaign or ad group level

The correct answer is: Making it a habit to upload four or more relevant and unique images at the campaign or ad group level

Explanation: When developing effective image assets, a best practice to follow is to regularly upload at least four relevant and unique images at the campaign or ad group level. This should ideally include at least three square images and one landscape image. Images with non-white backgrounds tend to perform better. Crucially, the most important content should be kept within the central 80% of the image and images should match those on landing pages for a consistent user experience. Opting into dynamic image assets simplifies this process by auto-pulling relevant images from landing pages.