Both The Downward Spiral and The Fragile by Nine Inch Nails contain lietmotifs.
Oh wow I completely forgot lol
I mean I'm reaching a bit with them because, at least for The Fragile, the motif isn't particularly connected to a certain character.
Red Headed Stranger -Willie Nelson
The german gothic rock band ASP created the album Zaubererbruder, which is entirely about the folk tale of Krabat.
The only thing I know with absolute certainty has a leitmotif (several, in fact) is Peter and the Wolf.
And maaaaybe Come to Daddy by Apex Twin. Does it count if the sound is literally generated by an image of the artist transformed into a WAV file? It literally represents them.
W.A.S.P.'s conceptual album "The Crimson Idol" plays with leitmotifs a bit: https://www.youtube.com/watch?v=qwnAzZF3_D8
Progressive metal is all about leitmotifs. Dream theater specially uses the technique to great effect. Like in Six degrees of inner turbulence or the meta album (each song in the album is in a different other album but construct a separate sequence) 12 step suite, about alcoholism.
I'll have to listen again but I don't recall 6doit having any recurring musical phrases that accompany characters or other ideas throughout the album. there is an overture at the beginning that introduces the songs.
It does, the overture doesn't only introduces later songs (through leitmotifs), it reuses them again for a reprise and a finale. Other examples include Metropolis part II: scenes from a memory, which is almost a musical, including characters, scenes and acts, and A change of seasons, where leitmotifs are not for characters but concepts.
A Thousand Suns by Linkin Park is a concept album about (nuclear) warfare and the threat of technology to humankind. It starts with an intro song in which the lyrics reference the penultimate song, The Catalyst. And that song itself has an intro track that references back to one of the first songs on the album, Burning In The Skies. The album connects itself back to front and the other way around.
Also, midway through the album, there's a track named Wisdom, Justice and Love, which features a speech by MLK, that gets progressively more distorted as it goes on, going from his normal voice to a completely robotic voice. In the intro to The Catalyst, the exact opposite thing happens, with the lyrics and melody going from robotic to natural sounding. Both these movements are a reference to the thematics of humanity vs. technology.
It's a masterful, underrated album. One of my favourites of all time.
Hospice by the Antlers and Diamond Jubilee both immediately came to mind, both albums have recurring melodies and interpolations throughout
The Dear Hunter, acts 1 through 5.