I have recently upgraded to 5.4 also. Now, none of the images in our galleries will display on the website, where they have been doing so very nicely for the last couple of years.
I only have Akismet plugin and loaded that after the upgrade. I noticed that the images were not loading prior to installation of Akismet, so it is not that.
I have also noticed many complaints in the support forums re: 5.4 so am assuming it has something to do with that?
We are using the Nestor theme.
