They are similar to the Town Fund in City Folk, when the player would hand over Pelly or Phyllis their given Bells. It would contribute to the town, to receive e.g. a bridge, fountain, and lighthouse or windmill.
The town decorations may have been an influence for New Leaf. As this idea could've been manufactured to create Public Works Projects, decorations that can be setted up by Lloid in town to be funded by the player or villagers. In fact, many of the decorations from Animal Forest e+ reappeared as Public Works Projects.
Town decorations that are marked with an "X" are of those that have reappeared in Animal Crossing: New Leaf as Public Works Projects.
The following three decorations could only be obtained via a code on the official website.