I have around 100 original photographs of Gatchina, Peterhof, Livadia and Tsarskoe Selo during WWII and afterwards. In Tsarskoe Selo I have many pictures of the pavilions and the great palace. I only have 10-15 of the AP. There are a few accounts in print of Germans in the palaces.
Susanne's book on Pavlosk is mavelous, but it does not tell the accurate story of what happened at the AP. Suzanne must have misunderstood what Kuchumov said. I have pictures that show the Imperial rooms on the lower floor on left side survived the war, they were a mess, but they were saved.
Peterhof and Tsarskoe Selo suffered differently during the war. The Great Palace in Tsarskoe was not destroyed by the Germans, it was destroyed by Soviet shelling. It happened over time. The Great Hall's roof went first, then later further shelling and fires destroyed more. For some time after the Germans captured it Peterhof was preserved and even had some furniture in it. Later, Peterhof was totally destroyed by shelling from Kronstadt. This shelling destroyed the English Palace and the Lower Palace. It heaviliy damaged the Peterhof Cathedral. I have many pictures of this. The palaces were used the the Germans or they were indifferent to them. Is it surprizing that German soldiers seemed to have no appreciation for the palaces? Well, Americans soldiers did severe damage to Babylon and the great minarets of Samara during the Irag war.
As to the Russian palaces, German and Spanish soldiers went in and out of them - except for the AP, which was occupied by the dreaded SS. No average German soldier could go in there. There were no 'tours'. There are few pictures when they were there and I don't have any. I have lots showing what the Russians found when they recaptured Tsarskoe.
WWII was a terrible awful conflict, which brought on the worst in everyone. The destruction was horrible. Millions died. The palaces were damaged because of the German invasion and they are responsible for what happened. It is terrible what happened because of the Russian shelling, but perhaps the military reasons for it would make sense if I knew them.