import re
regex = r"/([^\n]+)[?:\w-]+\.(gif|jpg|jpeg|tiff|png)"
test_str = ("<img src=\"https://www.gravatar.com/avatar/4cadbaae69c5c1c9b64b4370a7818a26.jpg?s=64&amp;d=identicon&amp;r=PG\" alt=\"user avatar\" class=\"bar-sm\" width=\"32\" height=\"32\">\n\n"
        "<img src=\"https://www.gravatar.com/4cadbaae69c5c1c9b64b4370a7818a26.gif?s=64&amp;d=identicon&amp;r=PG\" alt=\"user avatar\" class=\"bar-sm\" width=\"32\" height=\"32\">\n\n\n"
        "<img src=\"https://habrastorage.org/r/w1560/getpro/habr/upload_files/8da/358/d17/8da358d177ba245525e44e5ba2b43073.png\" data-src=\"https://habrastorage.org/getpro/habr/upload_files/8da/358/d17/8da358d177ba245525e44e5ba2b43073.png?asdf\" width=\"404\" height=\"405\">\n\n"
    )
matches = re.findall(regex, test_str)
print(matches)