Album Artwork won't stay large after sizing.
By hitting Command key and clicking icon at top of iTunes library, the artwork comes up. You can size it by right-clicking, but now, when you close out and hit another song, the artwork is small again. In the past, iTunes let you size the artwork and it stayed for all albums and even when it was shut off, the next day it was set. Can artwork be permanently sized. It gets big but shrinks back down after closing.
iMac with Retina 5K display, macOS High Sierra (10.13)