The seaweed shapes are taken from Matisse's paper cutouts, or decoupages. Matisse started making them when he was bedridden with cancer and unable to hold a paintbrush. Matisse had a studio in a southern region of France that is also part of Catalunya.
The pyramids and moon reference works by Alexander Calder, a Philadelphia artist whose father and grandfather were sculptors like him. For more about Calder, see calder.org. The blue star next to the moon is based on a Newsweek cover about Roy Liechtenstein, who has a large sculpture on display in Barcelona.
The ladder is Joan Miró's "Ladder of Escape," from a motif he invented during World War II. Miró fled Spain to escape Francisco Franco's dictatorship, which brutally suppressed the Catalan language and culture. A few years later, he also had to escape Paris when the Germans invaded in 1941. The ladder "represents the escape into pure creativity" (https://www.nga.gov/audio-video/video/joan-miro.html.)
This design is based on a mural Miró made for the UNESCO headquarters in Paris in 1968, called Moon Wall.
This green bird represents the monk parrots that roam Barcelona. The parrots used to be sold on Las Ramblas, a pedestrian street where vendors sell souvenirs and other merchandise. Either by accident or a conscious effort to set them free, the parrots were turned loose, and now live in flocks all around the city. The cutout shape of the bird symbolizes the parrots escaping the park.
The bull is a direct reference to Picasso's series of bull lithographs. He started by making a fairly realistic bull, and made the rest more and more stylized. Picasso lived in Barcelona during his formative years, and Spain always informed his art.
The design on the right end is taken from a 1990 Spanish stamp, also designed by Miro. Red and gold are the colors of Catalunya's flag, called La Senyera. This comes from a legend of a Catalan king named Wilfred the Hairy running his bleeding hand over his gold shield in battle.