Because this subject has no official name, the name "Hidden mural" is conjectural.

 Cave Drawings are found throughout Pikmin 3 and are small drawings of Pikmin doing various tasks. They are normally found in dark or not-so-obvious areas and cannot be seen easily. To see them, the KopPad is necessary. There are usually 2 per area. 

Locations

Tropical Wilds

  1. Found under the bridge built on the first day. Shows a pikmin carrying a 1 Pellet
  2. Under the Waterfall where the Mock Bottom is. Shows a Pikmin being chased by a Bulborb.
  3. Inside the hollow tree stump right next to the Seesaw Blocks. Shows a Red Pikmin near fire

Pictures of Drawings

Garden of Hope

  1. On one of the boards where Brittany is found. Shows Rock Pikmin breaking a Crystal
  2. In the pipe near where the Blue Onion is found. Shows a Rock Pikmin and a broken Crystal. 

Pictures of Drawings

Distant Tundra

  1. Inside the Tunnel under the Snowman with the Cupid's Grenade. Shows a Pikmin digging through a tunnel. 
  2. On a wall inside the Cave with the Pyroclasmic Slooches. Use the Bloominous Stemples. Shows Yellow Pikmin conducting electricity. 

Pictures of Drawings

Twilight River

  1. On the path up to the Scornet Maestro. Shows a Winged Pikmin carrying a Cupid's Grenade. 

Pictures of Drawings

Formidable Oak

  1. On the Reinforced Wall at the begenning of the Cave. If you have a picture of it, please put it here.