Hi Howard,
After investigating this issue, I suspect the cause of image not showing on the blog feature have something to do with your template. Please refer to the screenshot
When use joomla default template
http://screen.stackideas.com/Change_to_default_template.png
The feature image works fine and note that there is no additional class added on the image
http://screen.stackideas.com/current_template_001.png
When I use the traction template which you are currently using, the image does not display also take note the template will add an additional class on the image
http://screen.stackideas.com/default_template_with_class.png
Please consult with your template provided regarding this issue.
In future you can post all your site details here
http://screen.stackideas.com/default_template_with_class.png for security reason, thanks :-).
Hope that helps
.
Best regards
Chris