Getting unadorned image:
http://www.bing.com/HPImageArchive.aspx?format=xml&idx=0&n=1&mkt=en-GB
Can also use a bit of PowerShell:
irm "bing.com$((irm "bing.com/HPImageArchive.aspx?format=js&mkt=en-IN&n=1").images[0].url)" -OutFile bing0.jpg
[https://stackoverflow.com/a/42294596/7147183]
Previous images can be retrieved by increasing n
1 Apr 2021
https://www.bing.com/search?q=elephants&form=hpcapt&filters=HpDate:%2220210331_2300%22
20 JUl 2021
https://www.bing.com/search?q=moon&form=hpcapt&filters=HpDate:%2220210719_2300%22
24 Jul 2021
28 Jul 2021
29 Jul 2021
https://www.bing.com/search?q=international+tiger+day&form=hpcapt&filters=HpDate:%2220210728_2300%22
4 Aug 2021
https://www.bing.com/search?q=Clouded+leopard&form=hpcapt&filters=HpDate:%2220210803_2300%22
8 Aug 2021
https://www.bing.com/search?q=Elizabeth+Quay+Bridge&form=hpcapt&filters=HpDate:%2220210807_2300%22
9 Aug 2021
11 Aug 2021
https://www.bing.com/search?q=perseid+meteor+shower&form=hpcapt&filters=HpDate:%2220210810_2300%22
12 Aug 2021
https://www.bing.com/search?q=african+bush+elephant&form=hpcapt&filters=HpDate:%2220210811_2300%22
13 Aug 2021
https://www.bing.com/search?q=horned+ghost+crab&form=hpcapt&filters=HpDate:%2220210812_2300%22
23 Aug 2021
https://www.bing.com/search?q=little+blue+heron&form=hpcapt&filters=HpDate:%2220210822_2300%22
26 Aug 2021
https://www.bing.com/search?q=Glaucus+atlanticus&form=hpcapt&filters=HpDate:%2220210826_0700%22
28 Aug 2021
https://www.bing.com/search?q=red-billed+oxpecker&form=hpcapt&filters=HpDate:%2220210827_2300%22
30 Aug 2021
2 Sep 2021
3 Sep 2021
4 Sep 2021
https://www.bing.com/search?q=anna%27s+hummingbird&form=hpcapt&filters=HpDate:%2220210903_2300%22
19 Sep 2021
https://www.bing.com/search?q=red+panda&form=hpcapt&filters=HpDate:%2220210917_2300%22
23 Sep 2021
https://www.bing.com/search?q=neptune+planet&form=hpcapt&filters=HpDate:%2220210922_2300%22
29 Sep 2021
https://www.bing.com/search?q=wood+bison&form=hpcapt&filters=HpDate:%2220210928_2300%22
4 Oct 2021
https://www.bing.com/search?q=andromeda+galaxy&form=hpcapt&filters=HpDate:%2220211003_2300%22
8 Oct 2021
https://www.bing.com/search?q=common+octopus&form=hpcapt&filters=HpDate:%2220211007_2300%22
10 Oct 2021
https://www.bing.com/search?q=haliotis+iris&form=hpcapt&filters=HpDate:%2220211009_2300%22
13 Oct 2021
https://www.bing.com/search?q=Fossils+prehistoric&form=hpcapt&filters=HpDate:%2220211012_2300%22
19 Oct 2021
https://www.bing.com/search?q=madeira+laurisilva&form=hpcapt&filters=HpDate:%2220211018_2300%22
20 Oct 2021
https://www.bing.com/search?q=sloth&form=hpcapt&filters=HpDate:%2220211019_2300%22
21 Oct 2021
https://www.bing.com/search?q=Otter+lutra+lutra&form=hpcapt&filters=HpDate:%2220211020_2300%22
22 Oct 2021
23 Oct 2021
https://www.bing.com/search?q=eurasian+scops+owl&form=hpcapt&filters=HpDate:%2220211022_2300%22
29 Oct 2021
https://www.bing.com/search?q=raven+bird&form=hpcapt&filters=HpDate:%2220211028_2300%22
31 Oct 2021
https://www.bing.com/search?q=grotesque+architecture&form=hpcapt&filters=HpDate:%2220211030_2300%22
1 Nov 2021
https://www.bing.com/search?q=Dartmoor&form=hpcapt&filters=HpDate:%2220211101_0000%22
2 Nov 2021
3 Nov 2021
https://www.bing.com/search?q=world+jellyfish+day&form=hpcapt&filters=HpDate:%2220211103_0000%22
23 Nov 2021
https://www.bing.com/search?q=Ammonoidea&form=hpcapt&filters=HpDate:%2220211123_0000%22
8 Nov 2021
https://www.bing.com/search?q=polar+bear&form=hpcapt&filters=HpDate:%2220211108_0000%22
15 Nov 2021
https://www.bing.com/search?q=manatee&form=hpcapt&filters=HpDate:%2220211115_0000%22
23 Nov 2021
https://www.bing.com/search?q=Ammonoidea&form=hpcapt&filters=HpDate:%2220211123_0000%22
25 Nov 2021
https://www.bing.com/search?q=eurasian+red+squirrel&form=hpcapt&filters=HpDate:%2220211125_0000%22
3 Dec 2021
4 Dec 2021
https://www.bing.com/search?q=cheetah&form=hpcapt&filters=HpDate:%2220211204_0000%22
6 Dec 2021
https://www.bing.com/search?q=analytical+engine&form=hpcapt&filters=HpDate:%2220211206_0000%22
29 DEc 2021
https://www.bing.com/search?q=Oreamnos+americanus&form=hpcapt&filters=HpDate:%2220211229_0000%22
11 Jan 2022
https://www.bing.com/search?q=new+world+porcupine&form=hpcapt&filters=HpDate:%2220220111_0000%22
12 Jan 2022
https://www.bing.com/search?q=Mount+Fanjing&form=hpcapt&filters=HpDate:%2220220112_0000%22
27 Jan 2022
6 Mar 2022
https://www.bing.com/search?q=Great+cormorant&form=hpcapt&filters=HpDate:%2220220306_0000%22
20 Mar 2022
https://www.bing.com/search?q=Frogs&form=hpcapt&filters=HpDate:%2220220320_0000%22
27 Mar 2022
https://www.bing.com/search?q=Mothering+Sunday+uk&form=hpcapt&filters=HpDate:%2220220327_0000%22
10 Apr 2022
https://www4.bing.com/search?q=caracal&form=hpcapt&filters=HpDate:%2220220409_2300%22
31 May 2022
https://www.bing.com/search?q=Scarlet+macaw&form=hpcapt&filters=HpDate:%2220220530_2300%22
1 Jun 2022
25 Jun 2022
https://www.bing.com/search?q=brown+bear+ursus+arctos&form=hpcapt&filters=HpDate:%2220220624_2300%22
13 JUl 2022
14 Jul 2022
https://www.bing.com/search?q=Lemon+Shark&form=hpcapt&filters=HpDate:%2220220713_2300%22
29 JUl 2022
https://www.bing.com/search?q=international+tiger+day&form=hpcapt&filters=HpDate:%2220220728_2300%22
30 Sep 2022
https://www.bing.com/search?q=Southern+right+whale&form=hpcapt&filters=HpDate:%2220220929_2300%22
4 Oct 2022
https://www.bing.com/search?q=world+space+week&form=hpcapt&filters=HpDate:%2220221003_2300%22
5 Oct 2022
https://www.bing.com/search?q=world+teachers+day&form=hpcapt&filters=HpDate:%2220221004_2300%22
8 Oct 2022
https://www.bing.com/search?q=octopus+mollusc&form=hpcapt&filters=HpDate:%2220221007_2300%22
25 Apr 2023
https://www.bing.com/search?q=adelie+penguins&form=hpcapt&filters=HpDate:%2220230424_2300%22
31 May 2023
https://www.bing.com/search?q=sea+otter&form=hpcapt&filters=HpDate:%2220230530_2300%22