Some interesting calendars:

I know it's a bit late in the year for 2021 calendars, but I found a source with some interesting ones. I'll bet that Bob Parks would get a kick out of these two:

https://www.lulu.com/en/us/shop/brian-lockett/boeing-testbeds-2021-calendar/paperback/product-9jywj9.html?page=1&pageSize=4

https://www.lulu.com/en/us/shop/brian-lockett/boeing-prototypes-2021-calendar/paperback/product-rjnwrd.html?page=1&pageSize=4

 

Some interesting airline liveries on these:

https://www.lulu.com/en/us/shop/brian-lockett/heritage-airline-liveries-2021-calendar/paperback/product-y9m6ne.html?page=1&pageSize=4

https://www.lulu.com/en/us/shop/brian-lockett/state-flag-airline-liveries-2021-calendar/paperback/product-8jv8n5.html?page=1&pageSize=4

https://www.lulu.com/en/us/shop/brian-lockett/marine-life-airline-liveries-2021-calendar/paperback/product-8jvwwk.html?page=1&pageSize=4

https://www.lulu.com/en/us/shop/brian-lockett/novelty-airline-liveries-2021-calendar/paperback/product-2ek88z.html?page=1&pageSize=4

 

And if you like BIG airplanes:

https://www.lulu.com/en/us/shop/brian-lockett/martin-jrm-hawaii-mars-at-lake-elsinore-2021-calendar/paperback/product-zzw99d.html?page=1&pageSize=4

https://www.lulu.com/en/us/shop/brian-lockett/spruce-goose-howard-hughes-giant-flying-boat-2021-calendar/paperback/product-46jpn4.html?page=1&pageSize=4

https://www.lulu.com/en/us/shop/brian-lockett/antonov-an-225-mriya-2021-calendar/paperback/product-yk7v57.html?page=1&pageSize=4

 

Brian Lockett has also done some interesting books on the B-52 motherships that dropped X-15s and other experimental types, and a series on "flying aircraft carriers", the B-29s and B-36s that carried aircraft like the F-84K and the XF-85. All are available on lulu.com.