The dynamic image is very similar to the basic image element, but we use a placeholder in the editor and preview and generate an image element based on the URL given.
Dynamic images are the same as images in the output HTML, the difference is that you have to add to URL and the altText manually, and it must contain an expression.
You can set width and height to any value, but you have to make sure that you will use images with the same dimensions.
For example, if you want to attach everyone's profile picture you can add an empty dynamic image element and ESP will replace it with their pictures.
The image source needs to be replaced for the ESP to replace the images.
Let us know if you have more questions about this!