Create a recovery image of your current setup.
Restore a previous recovery image with wallpapers, then install Titanium, open it and tap scheduler and run either backup.
When it finishes, find your wallpapers under backup/restore and make sure they backed up.
Reload your Tranq backup from recovery, install Titanium, then restore your wallpaper under backup/restore. If you decide you like Titanium, tap schedule and check one of the scheduled items that matches your needs. The free version will only keep your latest backup.