Prior to #279 we had full size images in the activity stream which expanded beyond the confines of the column. It would be better to replace the image with a small placeholder image or a thumbnail.
It is possible that this might best be achieved by creating a wiki formatter for this purpose (see the thread culminating in bh-dev:01439).
Warning No events reported for enhancement: Images in activity stream should be indicated by a small image (new) in the last 30 days since Mar 26, 2017. This may happen if system is not configured correctly. Please contact your administrator if you think this is the case.