Talked with seth (link currently down) on IRC today about GnomeFileEntry. His thoughts were that it exists mainly for the “Unix Hacker” user profile, and thus shouldn’t be immediately visible in any decent apps, and where it is used, should look the same as it does now.
The three current instances of the file entry I see are: selecting sound files (in evolution and the control-center capplet), selecting a signature file to add (in evolution), and nested in various GnomePixmapEntry widgets. Except for the GnomePixmapEntry widgets (which should probably be a button, ala the old backgrounds selector), the case is accurate — they are used primarily for hackerish things.
So, GtkFileChooserEntry and GtkImageButton it is :-).
I must continue pestering andersca to finish the new GtkIconList widget so I can hack up the icon chooser again (I lost the dir with all the sources for that widget when I re-installed gnome 2.6 😦 ).