Would it make sense to use a RelationChoice for the banner_image?

[fulv]

Right now we have

    banner_image = namedfile.NamedBlobImage(
        title=_(u"Banner Image"),
        description=u"",
        required=False,
    )

Why don't we use a RelationChoice instead of a NamedBlobImage, or in addition to it?
What would be a good pattern?