Assuming your pictures are all the same size, place a frame on the master page.
Then choose File > Place and select all (or many) of your pictures at the same time in the Place dialog. You can multiple-select them. You'll see a number beside your cursor to indicate how many pictures are in your cursor. You can use the <left arrow> and <right arrow> keys to change what picture will next be placed. Move over the frame on the first page to click-place it. Move to the second page to click-place the second picture. And so on.
This works good, do you know if its possible to write a script to do this?