HDX 8.9 with 18.104.22.168.2. Rooted w/ Towelroot and have SuperSU installed. The HDXPosed module is installed and activated. Installed GPlay w/ KindleFree (wouldn't work with other methods and I'm sure I followed the instructions down to a T). Installed latest versions of Apex and Nova launcher. With Apex, I can only get the default wallpaper to show up; with Nova, can't use any wallpapers. Attempting to use any Live Wallpaper will lead to the "Live Wallpaper Picker has stopped" error. Attempting to use a wallpaper of my own by navigating to it via ES FIle Explorer leads to my selecting it successfully, but there's no change to the background.
Is this because I accidentally let the device update to 22.214.171.124.2? Seems like almost everyone else was able to change their wallpapers to their heart's content.
Edit: Saw a thread in the Android Dev forums, and one person recommended the "Image 2 Wallpaper" app. It worked beautifully. Still not sure why normal launchers can't change the wallpaper, though.