You can control the way your work is represented in an assignment topic.
When you attach more than one image to a post, the authoring tool automatically selects the first image to act as the “poster” for the entire post. As you can see above, this image appears on the front of your "card" in the grid view, and it's a sort of teaser for the full contents of the post.
Pick a New Poster
But the first image may not be the one you want to represent your work! Fortunately, it's easy to choose another image to serve as your poster: just click the poster icon on that image (see below).
HINT: As the instructor, you may want to ask students to select their most finished piece (or whatever criteria you specify) to represent their work.
Tell a Story
You can also rearrange your attached files by dragging and dropping their thumbnails into the right order. If, say, the images tell a story, you easily put them into the correct sequence.
Did your image load sideways or upside down? Use the rotation arrows to correct its orientation before publishing your post.