This question is an exact duplicate of:
Attempting to add a large (15MB) image to a post fails with no error message.
When I try to drag and drop the image into the "Add a picture" dialog, it just stays uploading forever. In Chrome's network tools, I see that the post to https://meta.stackoverflow.com/upload/image has been redirected to https://meta.stackoverflow.com/error?aspxerrorpath=/upload/image.
When I try the standard browse to add, the entire window is redirected to https://meta.stackoverflow.com/error?aspxerrorpath=/upload/image.
Shouldn't I see an error message letting me know the image is too big?
For reference, here's the image I was trying to add. (No idea why it was 15MB. I guess the Awesome Screenshot Chrome extension isn't so awesome.)