new backdrop settings dialog

[Brian J. Tarricone]

hi all-

i'm in the process of revamping the backdrop settings dialog, in 
preparation to adding a couple new features, and i have a mock-up of 
what i'd like to do with it.  the widgets aren't lined up nicely yet, 
and the sizing isn't how i want it, but i'd like to get some feedback 
before i go any further.  i put screenshots up at 
http://kelnos.homelinux.org/xfce4/#screenshots (click the thumbnails for 
full size images).  the 5 images are of the same dialog in different 
states.  the controls in the dialog change depending upon which option 
is selected in the "Backdrop Type" box.  aside from other possibilities 
(image preview, etc.), that's the basic idea for how i want to do the 
dialog.  what do you guys think?

    -brian