|Not sure about the luck implications of loaves standing on their ends...|
Apparently setting a loaf of bread upside down brings bad luck in France. The superstition supposedly dates from a custom of setting aside a loaf of bread for the executioner. In order to distinguish it from other loaves it was habitually set upside down. People don't want to be associated with the hangman, so they are careful to set their bread right side up. Supposedly, if a French person spots an upside down loaf, they will immediately right it.