Searching for images in media library returns incorrect results, how is that possible?

In our media library we have integrated a search function to search for images on the web. For this purpose we made the link with the search engine 'Bing!'. It is a fact that your search function produces the best results when using English search terms. Unfortunately we have no further influence on this. 

Did you already know that you can easily search for images without background by adding a space and then 'png' to your search term? For example the search term 'lion png' will show you images of lions without background.