In any case thought someone on HN might be able to point me in the right direction. Any help is appreciated! :^)
Not looking for anything specific beyond age, could be space stations, lunar / martian colonies or anything in-between.
https://en.wikipedia.org/wiki/History_of_science_fiction
For a modern view based on a relistic sense of rocketry, science, and technology, I'd probably start with the early 20th century. There were several popular works written by the 1930s, and I'd expect some from earlier.
Wikipedia's Space Colonization article suggests the work of Konstantin Tsiolkovsky, which I was also going to suggest, beginning around 1900.
https://en.wikipedia.org/wiki/Space_colonization
https://en.wikipedia.org/wiki/Konstantin_Tsiolkovsky
I'm not aware of specific illustrations accompanying these, but any such would all but certainly follow those dates.
The same article also suggests:
In the 1920s John Desmond Bernal, Hermann Oberth, Guido von Pirquet and Herman Noordung further developed the idea. Wernher von Braun contributed his ideas in a 1952 Colliers article. In the 1950s and 1960s, Dandridge M. Cole[18] published his ideas.
The Werner "who cares where they come donw") von Braun article was part of a series "Man Will Conquer Space Soon!'
https://en.wikipedia.org/wiki/Man_Will_Conquer_Space_Soon!
The series was reprinted in 2016:
http://www.aiaahouston.org/newsletter/
The age of American "pulp" science fiction magazines dates to 1926 with Hugo Gernsback's Amazing Stories. This and other early SciFi magazines are archived at the Internet Archive, and the covers are illustrated:
https://www.rbth.com/history/332103-soviet-space-colonizatio...