More placements methods for multiple screens

[Slypy06]

I will soon get a 4 monitor setup (2 vertical 16:9 monitors to make 1 big square monitor and two others horizontal 16:9 monitors) and I want to have 1 animated background spanned across the 2 verticals monitors and 1 other animated background spanned across the dual monitor setup. But I can only span the background across all the 4 monitors or une 1 background per monitor. It would be great if another placement method mixing the "span across" and the "selected only" were added or if we could select to which monitors we want to span the background with the "span across" option.

[rocksdanister]

Creating custom layouts is a good idea so that there can even be more than one wallpaper in a single screen.