専門的になりますが、よろしくお願いします。概略で結構です。お手数かけます。

Sticky recognition is created for photos of real-life stickers, like this one. The option finds box-like shapes on the photo and transforms them, like so:

You can remove suggested boxes or edit the contours. Click the box you want to modify and drag the corners. From one photo you can get several stickers, depending on how many box shapes the option finds.
Please see this example. As you can see here the option found most of the stickers (but not all of them):

So, unfortunately, it is just not for pictures of dogs, it is for pictures of stickers. A dog is not a rectangle shape, that is why the recognition does not see it.

You can add the pictures directly to the board though, just by uploading it from a URL link! Do you have any problem with that?