There are twelve ways of arranging the boxes without considering the pictures. 
If the thirty pictures were all different the answer would be 93,312. 
But the necessary deductions for cases where changes of boxes may be made without affecting the order of pictures amount to 1,728, and the boxes may therefore be arranged, in accordance with the conditions, in 91,584 different ways. 
I will leave my readers to discover for themselves how the figures are to be arrived at.