Yesterday I merged in the new Window Switcher Layouts implemented in QML. As before there are five available layouts but now it is easy to add further layouts. So I am waiting to see some new layouts. If a well-done layout is sent to me, I can include it in our default shipping till the artwork freeze. So use the chance to get your window switcher into our default offerings!
For the old implementation I tried to provide a preview at least for the selected layout and it was never working properly and I removed it again in a later release. Doing the same in QML took just a few hours and I am still a QML beginner.