Technically it’s not wallpaper but IKEA has a coloring poster called GETNÄS that ticks all the boxes on interesting visual impact. See how Medina of Grillo Designs did it. Your kids (or you) can progressively color it in too.
A surefire way to add some warmth to your entryway is to add some plants. The LURÖY bed slats hung on the wall becomes an effective vertical space for hanging plants. At your entryway, or really, anywhere you wish.