You like comics and you like wallpapers. Did you know that you can extract gloriously high res ones of the latter from the former?
First, you’ll need the comic in CBR or CBZ format. Both are simply RAR and ZIP files, respectively, with the extensions changed. Once you have that, simply extract the file using your preferred archiving tool (I recommend 7-Zip). This will spit out every page of the comic as its own separate image file, which you can then use as you please.