Steps to reproduce the issue

Prepare a folder in /images with many hi-res images, I used one with 1184 images with circa 2000x1500 px. Size 438MB
Just login to administrator of a Joomla 3.8.x site with permissions to manage media
administrator/index.php?option=com_media
and navigate to the folder mentioned

Expected result

List of image thumbs in that folder

Actual result

The result it's OK, I've just some observations in Additional comments section

System information (as much as possible)

You need a folder with many hi-res images.
I used one folder with 1184 images with circa 2000x1500 px. Size 438MB

Additional comments

This is not really a bug, just something to be aware.

All images in that folder are downloaded to show the thumbnails, In this case it took forever and 400MB.
I know this could be avoided by each item having his own images folder.
However, this is a real site, and the clients don't have the kind of knowledge we do and are usually difficult to predict.
It's my/our job to don't let situations like this occur. I can find a workaround in my end but this should be addressed in the com_media component.
I don't really have the answer but I'll leave some ideas:

• Pagination could help, but the problem remains(however less severe) if you have to navigate page by page to find the image.
• Pagination with search and/or ordering filter by relevant fields
• If images exceed value n force detail view only with file name, maybe fetch the image by ajax on mouse over
• A image cache with redimensioned thumbs, will need CPU power/time to resize first time.
• Could be optimized if we join some of the ideas, like cache and pagination.

This is my first time posting, Hope I'm not doing it wrong.

Keep up the good work guys.
Joel