Here we have a "no dogs allowed" sign in near the center of Helsinki. We notice that unlike the classical dog signs, this one does not depict a generic terrier, but a Big dog. Probably a german shephard.
Usage of big, possibly dangerous, dogs in signs can be a sign in itself. Here We notice that beyond the immediate messages conveyed by a selection of a big dog, the sign elements further support the idea of a possible danger as the dog is out of the bounds of the "No"-symbol 🚫.
Thus the message seems to be that "we don't want your big unruly dog in our backyard!".