The content jumps around because initially <img> elements have 0 height, the image loads and height increases, making content other "jump". The images are loaded when they are entering the viewport.

There are 2 options to solve that:

1. Define height of the <img> elements to be the same as the height of the image itself. The problem here would be retrieve that height.
2. Preload images. You can load all images before they are entering the viewport, that would minimize the jump. Here are some resources on how to do it: How to Preload Images without Javascript?