Documents are made up of a variety of story ranges or 'layers'. Inline graphics are in the text layer and will be accessed with ^g. Images that have a wrap option set are in the graphics layer and thus will not. You need to change the wrap to in-line in order to remove them by this method.
An alternative is to use a macro. The following should remove floating graphics
Code:
Sub Macro1()
Dim oShape As Shape
Dim i As Integer
For i = ActiveDocument.Shapes.Count To 1 Step -1
Set oShape = ActiveDocument.Shapes(i)
If oShape.Type = msoPicture Then oShape.Delete
Next i
Set oShape = nothing
End Sub