wallpaper vs wall mural

wallpaper and wall mural both are nouns.

Word	Noun	Adjective	Verb	Adverb
wallpaper	Yes	No	Yes	No
wall mural	Yes	No	No	No

As nouns, wall mural is a hyponym of wallpaper; that is, wall mural is a word with a more specific, narrower meaning than wallpaper:

wallpaper: a decorative paper for the walls of rooms
wall mural: A decorative printed wallpaper usually placed on only one wall; the print can either be custom or chosen from a predefined set.

Other hyponyms of wallpaper include mural wallpaper, photo mural, photo wallpaper.

wallpaper (noun)	wall mural (noun)
a decorative paper for the walls of rooms	A decorative printed wallpaper usually placed on only one wall; the print can either be custom or chosen from a predefined set.

wallpaper (verb)	wall mural (verb)
cover with wallpaper