see attached image, but basically having the images on the right side makes it so hard to "read" a post with an image, going back and forth with your eyes to "get" the whole post. So much easier to just put the images between the up-/downvote buttons and the text post.
I don't know if there's a reason for that besides looking different from similar sites. If so, I don't think this is the way, it really puts a strain on your eyes and our brain is not used to absorb information in this way.
Sorry to get your hopes up - it turns out that moving the image to the left is really hard (aka I don't know CSS grid very well). Also the other changes I wanted ended up being identical to "Compact mode" which you can enable with the cog in the top right. Highly recommended.