In Japanese 祝 means "celebration!" like celebrating 10,000 hits or something. Kind of a hard image to show the average Chinese person passing by on the street.

I am a Chinese. Here 祝 does not mean "celebration", but means "wish". The whole phrase means "wish something to sell well". But the artist does not state clearly what to sell. Here it is highest possible that the author wishes some artist's (maybe himself's) artwork (doujinshi) to sell well.