I currently have 2 image locations and they may the formats (jpg,jpeg,png,gif)
i.domain.com/simage.jpg thumbnail i.domain.com/image.jpg high quality i.domain
A little mixing did the job for me. Forced to download a CRX file instead of installing or displaying.
## Download crx location ~* \.crx$ { add_header Content-disposition "attachment; filename=$1"; }