First, I am not sure why you have HTML/CSS files both in master and gh-pages of github.com/dromerosalem/project-2: you can configure a GitHub Project Page site to get its files from the branch gh-pages (default) or branch master.
No need to maintain both branches: more on that below.
Second, I see in the HTML inspector of https://dromerosalem.github.io/project-2/ that the src/styles/style.scss#.home-body is never applied:

This is never applied:
.home-body {
  height: 100vh;
  width: auto;
  background-image: url(https://www.bouygues-es.com/sites/world/files/styles/image_background/public/2019-05/Mars.jpg?itok=upJry_B4);
  background-size: cover;
That explains the lack of picture: this .home-body class is supposed to be generated by Home.js
<div className="home-body">
  <h1>Welcome to Space!</h1>
The parent project IAmNini/project-2 (which you have forked) has:
Its index.html does call iamnini.github.io/project-2/bundle.js which includes the .home-body class.
As your project is organized (master and gh-pages identical in their content), your style is never called, because master never generated the right files in gh-pages.
Considering the parent project hes more recent commits than your fork, you might consider updating your master branch with the upstream one, and try again.