So why hadn’t I worked this out before? I hated that picture of the rocks and bit of ocean. The lavender field they changed it to wasn’t so bad. I have now customised my Windows 10 lock screen to one of my own images. It’s easy.
Click on the start button bottom left.
Select Lock screen in the left hand column
Select Picture in the drop down menu under the picture of your lock screen
Select one of Windows 10’s pictures or browse for one of your own.