King and Queen by Henry Moore used to overlook a reservoir as part of a sculpture park near Dumfries.
The guitar was used by David Gilmour on some of Pink Floyd's best-known albums, including Dark Side of the Moon.
Experts at Christie's say it is a foot sketch of the Libyan Sibyl, which was later painted on the Sistine Chapel ceiling.
The Imperial Winter Egg with 4,500 diamonds was commissioned by Russia's Tsar Nicholas II in 1913.
The 14-foot-wide mural by MF Husain sold for an unprecedented $13.8m (£10.6m) in New York last week.
The sale of 130 guitars, amps and pedals follows the star's death at the age of 78 in 2023.
The painting had not been publicly exhibited since 1977 and was sold at auction at Christie's.
The Sunday Afternoon painting is expected to fetch between £4m and £6m at auction, Christie's says.
The listing, which includes the artist's iconic costumes, platform boots and luxury car, could bring over $10m.
