This is my official series cover/poster for now! I'm pretty proud of it. There are a few reasons I made it the way I did.
The Scruffy Dude: He's the lead protagonist. I have him looking up, because despite being rather world-worn, he's still very earnest at heart. His spirit can still be captured by the wonder of what the universe can offer. Also, the readers will primarily experience this story through his eyes, so I wanted to have them as the focal point.
The Blue-Haired Elf: She's also a leading character. I have her with glowing eyes because a) she's manipulating magic, and b) it lends an air of other-worldliness and mystery to her.
Camera Angle: The high camera angle imbues some action and dynamism to the piece.
Space Setting: Makes it immediately apparent that this is a sci-fi story.
Magic Water: Hints that the sci-fi setting has fantasy elements as well. Also, it leads the eye around the figures to the focal point.
The Planet: The blue-ringed planet is the symbol of the Blue Star Rebellion.
