As of dbFront 188.8.131.524, you can simply change the subtype of the field to Url. You can then specify that the field should be shown as an iFrame in the Url tab.
dbFront will then automatically display the Url contents just below the field in an iFrame. If the Url appears to point to a Png, Gif or Jpeg, then dbFront will load the image into a Img tag.
The iFrame or Img will display full width within the column.
If the field is marked as read-only then dbFront will remove the Input field and only show the iFrame/Img with the Field label showing. To also hide the field label update the field layout to hide the label.