A dingbat or printer's ornament used to mark the end of a story in a newsletter or magazine is an end sign. It signals the reader that they have reached the end of the article. Some publications use simple shapes for an end sign. Other publications use a custom end sign that reflects the name of the publication or appears like a small logo for the company.
While the use of an end sign is not a rule, it's a good practice. It alerts the reader that the story reached its conclusion. Other options in place of an end sign are the use of plain or decorative rules separating articles or placing the article byline at the end of articles instead of at the beginning.