Critical views i hear from deniers are that there are no Armenian mass graves .. there are unsourced pictures most of them literally holocaust pictures and other falsified sources. Even a painting from a Russian painter from the 19th century (about a completely unrelated massacre). Is there anything to these claims?
That sadly is like asking about the Holocaust. There have been thousands of witnesses now lost since they died of old age in the 80s and 90s (a process currently underway for Holocaust victims). The genocide has however not been as well documented as the Holocaust, which the Germans scribbled down in the greatest of detail (and which still has deniers, mostly outside of Germany today).
The best source for such reports is possibly the museums dedicated to the genocide in Armenia, for example in Yerevan.
If you are still skeptical, that is understandable (though not necessarily reasonable).
Henry Morgenthau, American citizen and US ambassador to the Ottoman Empire during that time when the United States were still neutral, wrote about his time in 1918: "The real purpose of the deportation was robbery and destruction; it really represented a new method of massacre. When the Turkish authorities gave the orders for these deportations, they were merely giving the death warrant to a whole race; they understood this well, and, in their conversations with me, they made no particular attempt to conceal the fact."
And, if you want even the most valid of Turkish nationalist sources, take the word of Mustafa Kemal Atatürk: "The Great War massacres against the Armenians were shameful acts."
German (yes, the Turkish ally) ambassador to the Ottoman Empire Paul-Wolff Metternich recalled his time as followed: "In the implementation of its scheme to settle the Armenian Question through annihilation of the Armenian race, the Turkish government did not allow itself to be distracted"., as according to Israel Charney.
So while, like the Holocaust, the Armenian Genocide is doubted by Ultra Nationalists, there is no real historical doubt about the question whether it happened.
Well, I cannot say I am extremely well versed in the Armenian Genocide, but even a cursory search suggests plenty of well informed sources. The US ambassador at the time, Henry Morgenthau, was an eye witness to some of the attitudes and violence of the time, and his memoir, Ambassador Morgenthau's story, also contains photographs of remains of Genocide Victims. Here is a chapter: http://net.lib.byu.edu/~rdh7/wwi/comment/morgenthau/Morgen27.htm. As this sources makes clear, Morgenthau favoured a diplomatic approach to ending the violence. When he approached a German diplomat, the Diplomat's response was: 'I shall do nothing whatever for the Armenians,' which is very suggestive of the attitude at the time. So yes, there is conclusive evidence, and IIRC, there have been mass graves found, but someone more knowledgeable than I would be better equipped to explain that.
Sources:
Ambassador Morgenthau's Story H. Morgenthau, 1918.