For warehoused images, you can select the Warehoused Image option and provide a link to the image via the standard Link Dialog.
Additionally, you can add an Alternative Text.

In non Warehouse-Mode you can either browse to the particular picture or drag and drop it onto the image-well.

• Additional Content - opens the drop area for additional content as well as the following two sliders
• Vert. Position - sets the vertical position of the additional content to Top, Center or Bottom

• Position X, Position Y - Specify coordinates as top, bottom, right, left, center. The parallax image will be positioned as close to these values as possible while still covering the target element
• Speed - The speed at which the parallax effect runs. 0 means the image will appear fixed in place, and 10 the image will flow at the same speed as the page content
• Bleed - You can optionally set the parallax element to extend a few pixels above and below. This can hide slow or stuttering scroll events in certain browsers
• Height - Sets the actual height of the image display
• Z-Index - The z-index value of the element. By default it will be behind everything else on the page