Need help setting inline style from Gatsby

ArticlePost.jsx

import React, { Component } from "react";
import Link from "gatsby-link";

// This component pulls articles and lists them
class PostListing extends React.Component {
  
  // This fetches the frontmatter from the .md files
  getPostList() {
    const postList = [];
    this.props.postEdges.forEach(postEdge => {
      postList.push({
        path: postEdge.node.fields.slug,
        tags: postEdge.node.frontmatter.tags,
        cover: postEdge.node.frontmatter.cover,
        title: postEdge.node.frontmatter.title,
        date: postEdge.node.frontmatter.date,
        excerpt: postEdge.node.excerpt,
        timeToRead: postEdge.node.timeToRead
      });
    });
    return postList;

  }
  render() {
    const postList = this.getPostList();
    
    // This one variation of what I have been trying
		var cardBackground = {
			//backgroundImage: "url(" + this.getPostList().map(post => post.cover) + ")",
			//color: "red"
		};

    return (

      <section className={`row ${ this.props.containerClass }`}>
        {/* Your post list here. */
					postList.map(post =>
						<div className="col c4" key={post.title}>
							<Link className="card" to={post.path}>

								<ul className="tags">
									{post.tags &&
										post.tags.map(tag =>
											<li className="tag" key={tag}>{tag}</li>
										)}
								</ul>

								<div className="title">
									<h6>{post.date}</h6>
									<h5>{post.title}</h5>
								</div>
								<div className="overlay"></div>
                
                {/* THIS is where I need the inline style /*}
								<img className="thumbnail" src={post.cover} style={cardBackground}/>
							</Link>
						</div>

					)}
      </section>

    );
  }
}

export default PostListing;