NGINX image filter module

Can grav take advantage of the NGINX image filter module for on-the-fly image resizing? Would this be a good idea?

It can't take advantage of that. Grav has it's own webserver-agnostic image manipulation. - see the Media Docs

Right, I was just wondering if grav would be faster on NGINX if it used the native module.

Maybe a plugin could be written to leverage that, but I have no idea how it works so can't say for sure. Currently Grav doesn't know, nor care, what the webserver us that is serving it.

I thought a plugin for NGINX would be cool if it like doubled the speed.