I just made a simple Tasker lockscreen wallpaper changer for Galaxy S4 i9505 kitkat
1. Rooted phone
2. Tasker with Secure Settings
3. wallpaper images in any folder
4. Busy Box free for linux cp command (will explain later)
1. Create a folder on SD card with images you want to use for wallpaper. eg /sdcard/downloads/wallpapers where image filenames have naming convention: picture_x.jpg where x is a counter number starting with 1 eg picture_1.jpg, picture_2.jpg etc
2. Create a Tasker profile name eg. "Lockscreen wallpaper", set running time from morning hrs to late evening - thi is time when lockscreen wallpapers will be rotating.
3. Create a Taker task eg "Change Lockscreen wallpaper" containing-following commands:
a) add Variable Randomize with name %PICNO, min 1, max 100. 100 is number of your wallpaper image files.
b) I dont know why Tasker copy file was not able to copy file from wallpaper folder to system lockscreen wallpaper location (even root option was selected) but for this taks I had to use BusyBox cp command which worked ok.
Now wee need to copy our random image to temporary file we gonna use for lockscreen later:
Copy file from /sdcard/downloads/wallpapers/picture_%PICNO.jpg to /sdcard/downloads/wallpapers/temp.jpg
c) add Secure Settings -> Run Command:
cp /sdcard/downloads/wallpapers/temp.jpg /data/data/com.sec.android.gallery3d/files/lockscreen_wallpaper.jpg
check: use root and wait for process
d) add Wait : set to eg 10 minutes (will change your lockscreen every 10 mins)
e) add Goto Action number 1
4 Check it - launch you task , lock phone, unlock it. verify. Remember that changeing wallpaper will work when your phone is unlocked so new lockscreen wallpaper will be shown next time you wake your phone.