Lightbox, and the way discourse processes images and uploads them, are great.
We are running a forum about photography, so the way images are showed and how the system manages them is of great importance for us.
There are several things in the way the lightbox works that may be improved, from our point of view:
Show the images the biggest you can
Lightbox spares some space around the image that makes the image smaller than it could be showed in the available space in the container window. Minimizing that space would be great.
Let you show the image full size when there is more than one image
When there is only one image in the post, you can double click in the image and the image is showed full size, clipping it as neccesary.
But when there is more than one image, if you try to do expand it, you are driven to the previous or next image, you cannot show the image full size.
Image navigation should be limited to a zone in the left and right of the image, when you click in the center the image should be showed full size.
Don’t put anything over the image at least not something that stays there
When there are more than one image, small arrows are drawn over the image in order to navigate to the previous and next image.
That interferes the image visibility.
Navigation buttons should be shown outside image (if there is space) or should fade away after a few seconds of not moving the cursor.
A good example of what I mean is the way Flickr shows images when you expand it to full window.