Is there any filter available to set the naming convention of those auto generated thumbnails?
Something like this:
- thumbnail_150x150.jpg -> thumbnail-s.jpg
- thumbnail_300x300.jpg -> thumbnail-m.jpg
- thumbnail_600x600.jpg -> thumbnail-l.jpg
Seems that the answer is no...
I've followed the core functions and found a dead-end. And found this post ( How can I make add_image_size() crop from the top? ) where Rarst says:
In the function
And modified the beggining of the function
Much probably, all the code can be shrank to a bare bone, but this way we get the benefit of custom cropped images :))
This website almost explicitly provides an answer to your question: WordPress: Provide a Better Naming Convention for Thumbnails (I am in no way shape or form affiliated with this website. Just a little Googling for the answer)