Found on Russian Wikipedia. A more complete description can be found there.

The image is of a poster used to promote the film "Scarlet Sails" (Алые Паруса). The copyright is likely held by the film's producer. I believe the use of the low-resolution image to illustrate the article Scarlet Sails (film) constitutes fair use and that no free replacement is available.

The image is also used to illustrate the article White Nights Festival. The image is closely associated with the festival as it is reproduced on fliers and other promotional material in conjunction with the festival. Therefore the use of the image in the article constitutes fair use.