You can set the height of the bottom panel to 0 and that will get rid of it, but it will also get rid of the Shutdown button.
When you are creating a logon and you want the wallpaper to be full screen, with no top and bottom panels showing, set the top panel to "False" and the wallpaper will fill in that space.
The bottom panel default setting is 100 px. So if you have a 1280x1024 wallpaper, you need to crop the bottom 100 off of it and use it for the bottom panel, and the remaining 1280x924 image for the center panel. If you do it right, they will match and you won't be able to tell where they were cropped.
It's easier said than done...it takes some practice and trial and error, but that's all part of the fun.
