I recommend that you only load a small sized thumbnail for the blog post lists. I have seen the images struggling to load, not load at all and the whole post list page not loading because of the size of these image.
The image that I have magnified in the post list below, is 1000px x 624px. Please lower the size of these files and help speed up the blog manager. I also think loading 40 posts in the list per page is too much. I recommend lowering it to 25