Microsoft seems to be testing a new related image search box in the main web search results in Bing Search. I personally cannot replicate this, which I take as a sign that this is a test.
This was spotted by Khushal Bherwani who posted the following screenshot on X:
I think this is a clean-ish way for Bing to do this, but that is relative to Bing and how neat its search results may or may not be.
Forum discussion at X.
