According to Prismic one should use
"gatsby-source-prismic": "^4.0.0-beta.0" and "gatsby-plugin-prismic-previews": "^4.0.0-beta.16" and "gatsby-plugin-image": "^1.7.0", which I now use in my project. When I query the gatsbyImageData and pass it to a GatsbyImage component i get a 404 in the console. The image won't show if it's a jpeg or png, but a svg works, probably because Prismic has decided that svg:s are files and not images.
Anyone recognize this problem and has some input, will of course provide more info if needed.
Link to repo: GitHub - FagerKod/prismiclab