The Humming Chorus from Madam Butterfly is a vocalise piece, by Puccini
Another Soviet compatriot of Rachmaninoff, Reinhold Glière, composed Concerto for Coloratura Soprano in the vocalise style. This one's impressive to see performed, as it's a whole 11-minute concerto.
Holst's "Neptune" from the Planets Suite also had some wordless choral parts, but they're not as prominent as I think you're looking for; same for Grieg's "In the Hall of the Mountain King."
You can, of course, always look to the modern classical composers. While I'm not always a fan of what they do, they're certainly pushing the boundaries of music. Newer examples include Aeiou by Roomful of Teeth and Circlesong One by Bobby McFerrin, among others.
I assume you're also familiar with the style of sprechstimme, which was popular for modernist composers in France and Germany around the start of the 20th century. It's related to what you're looking for but not the same