Advice on removing backgrounds?

[carmen]

(09-17-2018, 05:18 AM)Ofnuts Wrote:

(09-16-2018, 08:53 PM)carmen Wrote: I am posting a first example of:
- kind of material I may start with (choosen because it was likely my very first project with Gimp, started in 2011)

Is there a full-size version (or at least a significant extract) somewhere?

I am sorry--the beginning of that cover project was so long ago,  I hadn`t learned yet to keep the largest/best original available. Here is the scan as just picked from archive.net
   
of which my original post was just a reduced version.
Googling for "Charles A Seltzer" "The Two-Gun Man" in images--standard when looking for book covers--you find only an edited version--cleaned of doodles and with some filtering. Of course, one of my reasons to reopen a cover project is bumping into an improved source. Unfortunately, they aren't so plentiful, especially for such vintage works (early 1900s): thus the fun.
Thanks!