When decorating your mantle you should always remember to keep it simple. Do not hang too many small family photos or wallpapers since they will look cluttered in the mantle. It is a good idea to have large pieces that can be viewed from a distance and they would make an impact instantly. If you want your mantle place to look more dramatic, you may consider putting bold candleholders as well as large vases.
If you feel like you should put family photos on the mantle place and then you have to choose the larger photos that can be viewed from afar. You have to consider using similar frames and it is a brilliant idea to add some decorative pieces once you hang your artwork in order to create a more cohesive feel to your mantelpiece. There is no outright rule to be followed when for placements on the mantelpiece.