Replacing the filename of randomly named files

Hi,

I have downloaded a few desktop background photos and they all have different names. I would like to rename them to a more distinctive name. All the solutions I found online for batch renaming are based on files with the same base (ie, IMG_001, IMG_002, etc) But this is my case:

636539955171427774-2018-02-11

a0539753-2bb6-4714-88f0-06e03f10e848

acf_blog_land83%90_index-04r22

AR-180219789.jpg&updated=201802120839&MaxW=800&maxH=800&noborder

de62c016-56de-4e75-9522-4c0ef6b757fa-getty-901753672

And the list continues. I'd like to replace them by:

BG photo 001

BG photo 002

Etc,

Does anybody know how to do this? I'd appreciate your help!