Hi there! I was born in 1987. When I was a kid (early nineties) I read this book and I LOVED the illustrations. I’m not sure if it was a modern book at the time or not.
It had lots of bright colors and I think very little white space. I remember lots of orange and pinks, and vividly recall one page where a character is walking up stairs, the stairs and the character are just black silhouettes. I think it was very geometric.
For some reason (and I don’t know if this is right at all) I have it in my head that it’s somehow related to a native people, like Aztec or something.
So, it’s definitely a children’s picture book, brightly colored with silhouettes, and geometric. Possibly to do with Aztec or some other native people.