I'm using nginx/1.10-3 on Debian.
I have a file named logo.img which infact is an svg.
I've modified /etc/nginx/mime.types to include the .img as an extension for the svg file type: image/svg+xml svg svgz img;
But the headers of the file served is still application/octet-stream
For some bizarre reason, i've been asked to serve the .img file as an svg for a logo on a site, i've got it to work on Apache2 using mime magic. But, as far as i know, that doesn't exist on NGINX.