Description of Problem:

The file selector doesn't have a preview of the
images. I think is annoying to everybody to need
to select a backgrond, change the actual
background and so have the preview. Is more
interesting see the image before change the desktop.

Steps to reproduce the problem:
1. Click with the right button on the desktop and
choose "Change Desktop Background"
2. Click "Add Wallpaper"
3. Select any png (or whatever) file.

Actual Results:

I think an image is more relevant. Please look at:
http://www.fisica.ufpb.br/~kelon/tmp/actual.png


Expected Results:

See this please:
http://www.fisica.ufpb.br/~kelon/tmp/new.png

How often does this happen? 

LOL. Until the developers change this :)

Additional Information:

I'm using gnome-control-center 2.6.1 on Debian
Unstable/Experimental. To get this working, I
think you'll need to use
gtk_file_chooser_set_preview_widget (). I never
used the gtk+, but I think thar function works. 
I'm an brazilian portuguese speaker, so I'm sorry
for my mistakes :(