So here is solution that i use both on my MotoX and Nexus9.
I run this app Wallpaper Changer
https://play.google.com/store/apps/details?id=de.j4velin.wallpaperChanger
Which allows me to point to a folder on my phone/tablet, to cycle through almost 40 images that I have created.
Settings wise:
I have found that using the "run as live wallpaper" option allows for much faster/smoother transitions & a slightly more optimal alignment of the image.
Additionally in the preferences I set the Image Position to "Fill" and Image Size to "Launcher" (Though as I said this is geared currently for a Nova Launcher with 3 screens)
I use a 3 screen home-screen setup so taking into account the scrolling I use this as a base.
https://drive.google.com/file/d/0B8E71a8hLgx1ZElSaVN2VGtlQTA/view?usp=sharing
This PDF that I threw together is based on my own much larger file with all my actual images in it. I have it setup with overlays for 3 screen scrolling Horizontal & Vertical for both the Nexus9 & the MotoX(2014)