English: Fresco of Kartorh Singh (left; alt. spelt as Kartoor Singh) and Sham Singh (right; possibly Sham Singh Narli, founder of the Singh Krora Misl, died 1739) from Gurdwara Baba Atal.
The Gurmukhi inscription reads: "ਕੜਤੋੜ ਸਿੰਘ ਜੀ ਸ਼ਹੀਦ (line break) ਸ਼ਾਮ ਸਿੰਘ ਜੀ ਸ਼ਹੀਦ"
Romanization of inscription: "Kaṛatōṛa sigha jī śahīda (line break) śāma sigha jī śahīda"
Source description: "The fresco depicts two legendary Sikh martyrs, Sham Singh and Kartoor Singh, who had sacrificed their lives for the Sikh faith. Both are dressed in the traditional warriors uniform and armed to the teeth with the traditional Sikh weapons. Sham Singh is older, Kartar Singh is younger. Both evoke images of Sikh valors, Sikh sacrifice and Sikh martyrdom. Kartoor literally means Hand Smasher, Kar-Toor." (quote taken from Panjab Digital Library)
The frescoes of Gurdwara Baba Atal are believed to have been originally painted around the mid-to-late-19th century (though photographer and author Satpal Danish, whom wrote a book on the frescoes, claims they were originally created during Sikh-rule), using Indian red, ochre and other earth colours with gold accents. However, almost all were repainted in a 1971 "renovation" in a very garish manner using artificial colouring and synthetic paint. Many of these frescoes have been destroyed, defaced, or deteriorated through neglect and harmful "renovations" since they were documented in photographs, especially on the ground floor during "kar seva" (renovations) in the 1990's.
Further reading on the life of Sham Singh Narli: 1) https://www.allaboutsikhs.com/biographies/sikh-warriors/the-karorasinghia-sardars/
2)
https://www.sikhiwiki.org/index.php/Sham_Singh_Narli