It is sufficient if we light one lamp in the sanctum of Perumal at home. If we desire, we can light one more lamp, nothing wrong with it. The lamp we light every day can be filled with oil and during special occasions, another lamp filled with ghee is lit up in a few households.
If the sanctum is big enough to accommodate, we can hang those photos under the photos of Perumal. The pictures of ancestors and Acarya-s can be placed at a lower level.