Sleazy Fork is available in English.
Shows just fullsize Image with hotkeys & without pop-ups on many image-hosting sites
there is no single universal "example image-sharing script", else I wouldn't have cases in my script and would be adding just @match@ lines
but I believe there is already a thing you requested functioning,
it's the default case - just add any website you'd like into @match or in options for handyimage to run on and it would display largest image found there.
Detect if the website is using an image-sharing script?
//@match http://*Detect if the website is using an "example image-sharing script", then load Handy Image script.