Would you be willing to answer a few brief questions about PlayStation Forums?
Just wondering if you can take screenlock wallpaper off, and leave it blank again?
Dont think you can, i would just suggest to make a all black jpeg and use that, or take a photo of like..your bed in the dark or a wall in the dark and use that.
if you go into settings>format>restore start screen image
it will place lock screen back to original wallpaper