I want to substitute data for images and documentation ive found suggests dragging the image-field tool onto the report. It says

"To add dynamic images to your report, use the content-field report element . The content field accepts different types of image inputs for rendering. The first approach is dynamically changing the image location within your dataset. If you have a field that contains a URL or file system location to your image, the content-field element will render the specified image."

Basically my data has values 'up' and 'down' and i want pictures of arrows instead of the words. From what i can tell, I should be able to amend my mysql query to replace 'up' and 'down' with urls of images? But this doesnt work...

The query looks like:- if(a < b,'http://www.....up.jpg','http://www.....down.jpg') as arrows

Then i dragged the image-field icon onto the report and changed the field value to 'arrows'

When running the report, nothing shows under the arrows column. Anyone know what Im doing wrong?