The above picture is not a cover (that I know of) but it shows the emotional tones I had in mind. I do have four covers saved for ideas, and I added one to this that was closest to what I had in mind.
My story is an adult (supernatural) thriller. The trends I noticed were either simple imagery of one scenery shot and a big, bold text across the image, or no image at all and heavy, dark colors. There were a lot of blues and shadow accents around the images. When I looked at my subgenre, supernatural thrillers, the covers got busier, playing on their specific theme of the story, or almost completely black with big bold text. People were hardly in any covers, usually just a silhouette or side-profile in the distance, if any.
Some symbols for my book include darkness, rain, forests, guns, valentine's colors, a child's rainboot, smoking.
Some themes for my book include: Fear, loss, grief, desperation, mystery, and in general, running from your problems.
Cover colors: I want a darker tone, but a forest plays a big part, so saturated earth tones, like dark greens and a dark grey sky might be it. I also liked the thought of having something bright in the focal point to contrast this dark background.
Snapshot: This is a mystery, and I want to lean into that. My original idea for a cover was busier to hint that it is a supernatural story. I want to cut all that down to just one symbol to pull the readers in. They know something happened, like something dark from the tone, but they want to figure out what.
10: I have a few variant ideas for my cover, all working around the same ideas. Its hard because I like so many things and I'm a visual learner, but I'll probably know what I want when I see it. The cover I posted came closest to my ideas, but I have 4 saved.
1. A dark green pine forest across the background, with the grey cascade mountain range behind it. In the foreground, a little girls rainboot, scuffed and leaning on it's side. Its white and pink, with little hearts all over it. Shadows along the edges of the image, and the title at the bottom.
2. A similar background, but blurred and maybe no mountains. A little girl stands in the foreground, reaching out. She has a pink raincoat on and the boots, but her face is blurry.
3. For a simpler idea: The background is mostly a black silhouette of the pine forest, with a starry night above. In the foreground, the rainboot is almost glowing and more detailed: white, pink, red, little hearts, etc.