Images are looking good in all device except mobile...

Just had another thought. If you are using Image Fill for this shape object, make sure your image has been resized to the exact height and width required for the shape before you import it into Captivate and apply it as the fill for the shape.  There may be some difference in the way the browser on some devices render the CSS that is being applied to achieve this image fill. Making sure the image is exactly the same size as the shape should mean that the image undergoes no rescaling and could make a difference to the clarity.