Internet Explorer DOM7009: Unable to decode image

I'm working with a SharePoint site in O365. The site includes a List/Library that contains nothing but employee images with .GIF extensions. A 3rd party process imported the images into SharePoint. I have no details on that process.

None of the images will display in IE 11 when served from the SharePoint O365 server. The image will not display even when loaded by itself. The problem is not related to the amount or size of the images as this question discusses. The same exact images will display fine in IE 11 on an on-premise SharePoint 2010 server. Chrome, Firefox, etc display the image fine on both servers. I do not see this problem with any other browsers nor do they give any warnings or console errors. It's purely related to IE 11 and these .GIF images on the O365 server.

IE shows the following console message for each image:

DOM7009: Unable to decode image at URL: [url]

How do I fix this problem and what could be causing it?

Edit: If I simply save the image from the web and try to open the image via IE, it fails to display with the same issue. If I save the image that is displaying properly on-premise and try to open it via IE, it fails as well.

Headers: http://pastebin.com/vHhs4rm6

My Solution:

If I opened MS Paint, created a new .GIFF image and saved it to my server, it would actually display properly.

This led me to use ImageMagick and do an identify on the images that wouldn't display. ImageMagick indicated the images were originally PNG's and were saved to my server as GIF's for some reason. Renaming the image files back to their native format via a workflow resulted in them being displayed properly. So, whatever process uploaded all the images to my server renamed PNG's to GIF's, messed up the files and resulted in this problem.