Here's a list, with the first column being the in-game name, the second being the description of the real piece, the third being a description of the fake:
Ancient Sculpture A short metal idol Fake has eyes with pupils.
Animal Sculpture Two boys suckling a wolf Fake has one boy.
Beautiful Sculpture Topless woman with no arms Fake has long hair.
Great Sculpture Warrior in yellow Palms are facing downward in fake.
Mystic Statue Egyptian bust Fake has a round head, not flat.
Manly Sculpture Nude man Fake has a cloth over both shoulders.
Robust Sculpture Discus throwing man Fake is holding a flying saucer.
Valiant Sculpture Winged sculpture, no head Fake has bat-like wings.
Amazing Painting A man in white, and black Fake, black is left, white is right
Basic Painting A man with his hand on hip Fake has both hands on hips
Dynamic Painting A wave Fake has Mt. Fuji under the wave
Famous Painting Mona Lisa Fake has left hand on top
Jolly Painting A man with a vegi face Fake has a carrot with green spout as nose
Good Painting A basket of fruit Fake has a fly on the fruit
Quaint Painting A woman in a yellow shirt Fake has no white bonnet
Moving Painting Venus in a shell Fake, shell is closed
Supple Painting Woman in a red kimono Fake, her head is looking to the left
Serene Painting Woman holding a white ermine Fake has a cat instead of a ferret
Scary Painting An angry man Fake has long index fingers pointing right
Solemn Painting A girl in a white dress, sitting Fake has a girl standing up and tall
Wild Painting A black and white figure Fake has white on right, black on left
Wistful Painting Women in blue and white bonnet Fake has an orange bonnet
Common Painting People working in a field No fake
Fine Painting Red dog with two people No fake
Flowery Painting Sunflowers No fake
Gentle Painting People in a park No fake
Moody Painting Man with blue plants, crops No fake
Nice Painting Red pants, playing flute No fake
Perfect Painting Painting of apples No fake
Proper Painting Woman with a white collar at bar No fake
Scenic Painting Snowy forest No fake
Warm Painting Woman on a bed No fake
Worthy Painting Woman and French flag No fake
Alternatively, you can check this gallery here (which is rather too large to directly link each image).
If you want to research yourself, the Animal Crossing: New Leaf Instruction Manual also has a section named "Artists and Sculptors" where it lists the actual name of each piece of art in the game. For example, "Wistful Painting" is *The Girl with the Pearl Earring" by Johannes Vermeer. You could then look the image up in a search engine and compare it with the image ingame.
Note: I have the eShop version of the game, so I'm not completely sure that section is in the physical manual.