Helion - book cover and sketches

This is art for our (my husband and me) self-published book. The story and world are bit eclectic in way as Final Fantasy, so I decided to make cover similar to space opera posters :) Also there's some concepts of world's features
The book is aviable on Russian:
https://author.today/work/19352
Also here's previous illustrations:
https://www.artstation.com/artwork/YERqX
https://www.artstation.com/artwork/5R9bP

Rough sketch of battleships for cover

Rough sketch of battleships for cover

Helion's rings of islands

Helion's rings of islands

Warrior of high-ones

Warrior of high-ones

Ogrid from Junk ring

Ogrid from Junk ring