This picture is have some mistakes. I am a muslim and I go to mosque every friday, and I want to inform you there no marbles on the floor. Turkish mosques are covered with carpets. Also the jannisaries never forced to convert Islam. Because they are slaves and Ottomans did'nt care their religious beliefs. 

Janissary doesnt mean "soldier of victory". That is not "yeniç(there is no such wor 'yeniç' in turkish) eri(that means 'man' in old turkish but we use it now for soldiers)" , that is "yeni(new) çeri(soldier)".  You can look here: [Dictionary(Officam Turkish Goverment Dictionary)]