It displays for me, did you do something to fix it? (e.g. submitting the picture again, as it can happen if one closes the page just after submitting the picture, in such case the thumbnail may not be generated as it is generated while loading/displaying the confirmation that the image was set)
Or was it a temporary issue?
Is this a recent screen capture or a problem from yesterday?
Do you still encounter errors 503 or missing pictures in general after the few fixes I mentioned today here above?