Access the template you are working with and create a custom label and its image resource. This article explains how to create custom tags and resources.
Copy the name of the custom tag from Athento and go to Jasper.
In Jasper, create an image.
Click on the created image and access the Properties option. In the expression editor you must put:
In the above expression, replace "custom-tag" with the name of the tag you copied in Athento.
Now you must create a parameter
Select the "Create Parameter" option and in "Name" paste again the name of the custom label.
In Jasper you can specify the size of the image with the width and height options: