The look and feel of attachments on item details is now completely revamped. It now presents a bigger image thumbnail. Also, the layout has been cleaned. Please note that the preview of existing images remains in the original size. New attached images have the new and bigger preview.
Please note that for image attachments uploaded before this feature was implemented, thumbnails were created with the width 100px. For new images thumbnails are generated with 260px width to fit better. So, old thumbnails will look a bit small in the new design.