Hi,
If i add a preview image, would this help by loading and decoding more quickly maybe, waiting for the full res to display?
No, that 'decoding' is something that the browser does internally and which is not controllable by own code.
Decoding itself means e.g. decoding the jpeg bytes to the actual image pixels. And during that decoding the browser is blocked. Larger images need a longer decoding time and smaller ones. When the decoding is faster than one frame time (e.g. below ~15ms) then there will no visible interrupt.
Best regards,
Klaus