windowscentral[.]com/microsoft-releases-dogs-and-cats-wallpaper-pack
microsoft[.]com/en-us/p/dogs-and-cats/9pfhf0wtsq72?irgwc=1&OCID=AID2000142_aff_7593_159229&tduid=(ir__wr3zcfpre0kftxorkk0sohznxf2xlyvz6tsol9et00)(7593)(159229)()(UUwpUdUnU73720YYwYwo5uw4zdpo5zwgzloorzgc3bomnxw2)&irclickid=_wr3zcfpre0kftxorkk0sohznxf2xlyvz6tsol9et00&activetab=pivot:overviewtab
The 2nd link, from the Windows Central article, is to the Microsoft Store, where all their win10 Wallpapers are now released. FWIW, it's a slight PITA, but if you install a wallpaper pack, then you can export that theme via Settings, than unzip the result to get the individual images.
Note: Just a reminder, the often changing win10 lock screen images from Microsoft are stored here: C:\Users\ [UserName]\ AppData\ Local\ Packages\ Microsoft.Windows.ContentDeliveryManager_cw5n1h2txyewy\ LocalState\ Assets\
The files names look like just a random string of characters with no file extension -- you have to rename each one to something with a .jpg extension, then open it to see what you've got. There are usually a few full-screen images, a few cell phone images, and a few icons, the 1st two changing often as Microsoft pushes out new content.