Is there any way to provide our own thumbnails for the file types that the system already supports?

I want to provide my own thumbnails for the file types which System already provides thumbnails for. I tried using QLThumbnailProvider however it works only when the file type is custom. For system supported file types it doesn't allow me to override my own thumbnails. Is there any alternative to this?

Is there any way to provide our own thumbnails for the file types that the system already supports?
 
 
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