Problem with wordpress gallery

Hello, I´m having a few problems with wordpress galleries using Safari in all devices and with iphone and ipad with all navigators. Some of the images can´t be viewed, not all. Instead of the images I see the name of the file and a white square. With other devices or OS I don´t have any problem. I hope anyone can tell me what can I do. Thanks. My website is http://concurso.avium.es