documentclass[11pt,ngerman,a4paper]{scrartcl}
usepackage[utf8]{inputenc}
usepackage[printwatermark]{xwatermark}
newwatermark[allpages,picscale=1,picfile=./bg1,picfileext=png,picwidth=210mm,picheight=297mm,xpos=0,ypos=0]{}
begin{document}
    Hello World!
end{document}

documentclass[11pt,ngerman,a4paper]{scrartcl}
usepackage{background}
backgroundsetup{
  contents={includegraphics{bg1}},
  scale=1,
  angle=0
}
begin{document}
    Hello World!
end{document}

usepackage{xcolor}

usepackage[printwatermark]{xwatermark}
newwatermark[allpages,picscale=1,picfile=./bg1,picfileext=png,picbb=0 0 100 100]{}

newwatermark[allpages,picscale=1,picfile=./bg1,picfileext=png,]{}

newwatermark[allpages,picscale=1,picfile=./bg1,picfileext=png,picbb=0 0 597.432pt 845.0772pt]{}

documentclass[11pt,ngerman,a4paper]{scrartcl}
usepackage[utf8]{inputenc}
usepackage{xcolor}
usepackage[printwatermark]{xwatermark}
newwatermark[allpages,picscale=1,picfile=./bg1,picfileext=png,picbb=0 0 597.432pt 845.0772pt]{}
begin{document}
    Hello World!newpage
    Bye-bye!
end{document}