Genre conventions are a contract with readers
Each genre has a visual dialect. Thrillers: high contrast, desaturated palettes, isolated figures, bold sans-serif titles. Romance: warmth, soft light, couple or symbolic-object imagery. Fantasy: rich saturated worlds, ornate detail, atmospheric scale. Literary fiction: restraint, abstraction, negative space. Prompt inside your genre's dialect — a cozy-mystery cover with horror lighting confuses the exact readers you need. Browse your subgenre's current top 20 and name what you see; that observation becomes your prompt vocabulary.
Design at thumbnail size
Your cover's most important rendering is about 100 pixels tall in a store search grid. One strong focal element, clear silhouette, and title-friendly composition beat intricate detail every time. Prompt explicitly for type space: "dramatic lone figure lower third, moody negative space upper half for title". recraft-v41 is the standout model here — it composes like a designer and can render clean title typography directly, though many authors generate the artwork and set final type in a layout tool for full font control.
From ebook cover to print wrap
Ebook covers commonly ship around a 1.6:1 height-to-width ratio. Print adds real constraints: your artwork needs to reach 300 DPI at trim size plus bleed, and a full wrap needs coherent art extending across the spine and back. Generate large, then run Nidhogg's upscaler before print export — and check your cover at both extremes: crisp at print resolution, instantly legible at thumbnail.