Lazy load is great. But it would be nice for user experience to see better placeholders (I'm aware of the filter, but it's not enough), I'd like a unique placeholder for each image.

Two techniques come to mind:

1. Predominant color placeholders:
   Shows a solid image of the predominant color, used by Google images, example:
   

2. Low quality placeholder:
   Consists on using a small pixelated version of the real image and apply a blurry CSS filter to it.
   Details: https://jmperezperez.com/medium-image-progressive-loading-placeholder/

This is probably wishful thinking, but was worth asking for. Thanks!