Inserting photos into video

Within a music video, I want to insert some photos into the video timeline that go along with the song. The issue is that when I do insert photos, they insert just fine, but they displace the video (extending its time length) as well as the audio track. It is easy enough to drag the audio back over the blank space in its timeline, but now the audio and video are out of sync after the point where the photos have been inserted. I want the photos to overwrite the video so that I do not need to determine how much video to cut out. I figure I am doing this all wrong from the get go, so perhaps there is a technique or setting that gets around all of this.