Praise be to Allaah.
You have to hasten to remove these pictures at once, because it was reported that the Prophet (peace and blessings of Allaah be upon him) strongly forbade hanging pictures, and he commanded his great Companion ‘Ali ibn Abi Taalib, “Do not leave any picture without blotting it out and do not leave any built-up grave without levelling it.” (Narrated by Muslim, 1/66). Hanging up pictures of animate beings deprives the people of that house of a great blessing, which is the entrance of angels into that house. It was reported from Abu Sa’eed al-Khudri (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “The angels do not enter a house in which there are statues or pictures.” (Narrated by Imaam Ahmad; see also Saheeh al-Jaami’, 1961).
You can replace them, if you wish, with pictures of inanimate objects, such as trees, mountains, oceans and other natural scenes, or other drawings of inanimate objects, without being extravagant or wasteful.
As for the pictures which are hanging, you have to remove them and blot them out or burn them; do not keep them. It is worth noting that hanging up pictures of the dead is one of the things that renews grief and serves no useful purpose; it may even lead to some kind of veneration which goes against Tawheed. Let us not forget that the shirk committed by the people of Nooh (peace be upon him) started because they set up pictures and images of some righteous people who had lived among them. So be very careful. May Allaah help us and you to do all that pleases Him and earns His forgiveness. And Allaah knows best. May Allaah bless our Prophet Muhammad.