Rev. David P. Murray of the Free Church of Scotland (Continuing) in Stornoway has a series of videos hosted at Sermon Audio. I’ve only watched one, Christ in the Covenant With Adam from the Christ the Covenanter series. I must say, I enjoyed watching it. The videos are of lectures dealing with various aspect of theology and Christian living. Rev. Murray is the lecturer in each video, from what I can tell. I recommend checking them out, they would be very useful for Sunday School.