montage vs paste-up

montage and paste-up both are nouns.

Word	Noun	Adjective	Verb	Adverb
montage	Yes	No	No	No
paste-up	Yes	No	No	No

As nouns, paste-up is a hypernym of montage; that is, paste-up is a word with a broader meaning than montage:

montage: a paste-up made by sticking together pieces of paper or photographs to form an artistic image
paste-up: a composition of flat objects pasted on a board or other backing

Other hypernyms of montage include icon, ikon, image, picture.

montage (noun)	paste-up (noun)
a paste-up made by sticking together pieces of paper or photographs to form an artistic image	a composition of flat objects pasted on a board or other backing