The Image question type is exactly as advertised. Display an image in your survey by pointing this question type to the absolute URL (e.g., http://www.your.com/image.gif). You can optionally include a caption to describe the image.
Example
When selecting a question or content type, you can see what you're getting before you make your decision! Click on the Examples link at the top-right of each question type box. You'll get a brief preview of what the type looks like and how you might use it.