Create new endpoint for another image size - (for new BIE)

[kylie-m]

Could we please create a new endpoint for an additional image size?

Background - It's to support the new Species pages (Atlas index)

Proposed size is xxxx x 800 px (preserving aspect ratio) - TBC

@adam-collins this is based on our meeting yesterday, did you need a specific size? Or have any other thoughts or additions? thanks

[adam-collins]

This was to be used instead of /original for a full screen slideshow