Bing is testing a new layout for Multimedia Ads in search results, replacing the previously used landscape images with square images.
The new format takes up less space on the search results page, making the ad placement appear more compact. However, the placement still displays only one ad at a time, as in the previous layout.

This is another recent test of Bing’s Multimedia Ads placement. A separate test was recently spotted moving Multimedia Ads to the center of search results, suggesting Microsoft is experimenting with both the position and appearance of these ads.
This update was shared by Khushal Bherwani.