In 2.4 I at least found no no 'disableFileDelete' kind of option for the ImageField. But if you were to block the FileIframeField.js from the requirements, it would prevent the popup, and just immediately unattach the image, without deleting it (which seems not so bad, since you can always re-attach it if you wish).
So you could maybe extend the ImageField to 'BannerImageField', and override the function iframe() (copy it from the FileIFrame class) and block the FileIframeField.js from loading...
Other options:
- present a simple dropdown of banner names from the
- use a treedropdown
- use a radiogroup with banner-image thumbnails
Hope this helps - but I've not needed this before, so others might have far better solutions... :-)