You can get separate wallpapers using the standard NVidia drivers: NView -> Desktop Management -> Desktops -> Properties -> Allow different backgrounds per display.
Probably doesn't solve the icon problems though, and the monitor-specific toolbar of Ultramon looks good. (I do like NView's...
I've you've got an Nvidia graphics card, try enabling and editing the Nvidia Settings -> Desktop Management -> User Interface -> Edit Gridlines.
This does exactly what you want - you can setup gridlines to divide the screen up (arbitrarily - horizontally / vertically / evenly spaced or not)...