Neville, Ginny and Luna are being held in three separate cells in the Hogwarts dungeons. The Gryffindors have spent their confinement shouting themselves hoarse to no avail, while Luna has been using her food to fingerpaint the walls of her cell to resemble a bright cheerful garden of flowers. Before they leave, she uses magic to make the paint job permanent:
“I just focused on wanting it all to stay forever so the next person doesn’t have to be depressed.”
We should point out that Luna's wand had been confiscated, so she performed all this using a spoon as a substitute.
Neville's return from the forest...with the whole school, even the Slytherins, saluting him and his companions.