If you look in the Internals Toolbox sample projects folder inside the SuperCard application folder you'll find a number of XFcns (InsertFieldObject, InsertFieldHyperLink, GetSetObjectBaseline, GetSetObjectImage, GetSetObjectName, GetSetObjectProp, GetSetObjectRefCon, FlattenFieldHyperLink, SetObjectPlacement, TestObjectAccessors) that let you insert images into fields and query/tweak their properties.
There's also several example projects, which hopefully should be fairly self-explanatory.
HTH,
-Mark