[MisterT2000]

Do you see the disc art in other views? If so, what is the view name where you don't see it?
If you don't see it nowhere, it's likely you didn't scrapped it.. To make sure of that, select the Alien set, go inside, select one of the alien movies, go to contextual menu, select "obtenir le logo/clearart - mode GUI", then select DISC ART, and select the one you like.
Now, do you see the disc art for this movie? If not there is a problem i don't understand.
If yes, go one step back to put yourself at the set level. Do you see the disc of the movie you just scrapped?

thanks for this little tutorial djoole with french sentence. It works now. I have all discarts in m y alien set. I think i'll modify the size and position of discarts for more visualization. But i don't understand why Artwork downloader addon doesn't scraped discart because in settings artwork downloader addon, discart is check. Or discarts must be manually add?