So it seems to be a missing icon.  This is the same as in normal
 customisation buffers in which I only see the [reset] button, but not
 the [set], [save], and [done] buttons (this is 21.5-b9).
 
 Is anybody else noticing this?  IIRC, there was a discussion once
 about this. 
What's supposed to happen is that if you have widgets you see the 
graphical thing, if you don't you see the text version. The widget
version is supposed to subsume the pixmap version that was there 
before. What I didn't do was try and fallback through 10 different
graphical properties. 
andy