Are you using Filemaker's Label wizard? I suspect that it is inserting your field as merge text. In layout mode, you'll see it in this format: <<field name>>.
In layout mode, double click the text and delete the above reference to your picture field. Now use the field tool to drag and drop a new field on your label layout. Select your picture field for this new field. Now reposition/resize any other fields on your label layout that are still shown as merge text to get what you want. Check final results by previewing.