Yes, via ifile. Just copy the file of the wallpaper you like (you'll find it under var/stash/themes.../edius.theme and then you'll see files like LockBackground@2x.png and Wallpaper@2x.png and so on. Hit edit, select the one you want, then tap the bottom right of your screen (looks like a double file) and hit copy. Back out of that folder and then find the folder of the theme you like and paste this in the folder with the wallpaper you want to replace. Delete the file with the wallpaper folder and rename the file you just pasted with the exact same name of the file you deleted.
Or if you just want the wallpaper and aren't using a theme, open the Wallpaper@2x.png file or whichever one you like, hit the little icon at the bottom that is 3rd from the left and send it to your photos. Then make it your wallpaper.