His friends have some pictures of him and he has asked them to destroy them, but they refused

Praise be to Allah.

Allaah erases sin by means of sincere repentance from sin, as Allaah says (interpretation of the meaning): 

“And all of you beg Allaah to forgive you all, O believers, that you may be successful”

[al-Noor 24:31]

And the Prophet (peace and blessings of Allaah be upon him) said: “Islam destroys that which came before it [of sin], and repentance destroys that which came before it [of sin].” You have to destroy the pictures that you have, because the Prophet (peace and blessings of Allaah be upon him) said to ‘Ali (may Allaah be pleased with him): “Do not leave any image without blotting it out and do not leave any elevated grave without leveling it.” Narrated by Imam Muslim in his Saheeh. With regard to the pictures of you that other people have, if you ask them to return them and they refuse, then you are free from any blame and your sincere repentance includes these pictures too; the sin is on those who are keeping them. May Allaah guide us all.