how did my MOJAVE default login screen image of the desert change?

Every day since I upgraded to Mojave, the default login screen image of the desert appeared. Then, I BELIEVE, after upgrading to 10.14.6, it changed. Can anyone tell me how to get it back to the default image, and stay that way?

side note: my mini is the 2012 version, but that device was not listed on the list to choose from.

Thank you to anyone that can help with this question.

OR, is this a moot point, since the default login screen will change again under CATALINA?