These are 7 aquarium decoration pieces from Japan and are likely from the 1950s and 1960s. 

One is a 4-inch-high castle tower with a tree; two are a matching set both with castles, trees and are painted with subdued colors; two are a set of arches with one building on each one, and the final two are large pagodas with more vivid colors. 

The two pagodas stand about 4 1/2 inches and the shortest piece in the entire 7-piece set is 3 2/3 inches tall. 

Using them all would work just fine and they are all depict a Japanese theme and all the colors are very similar. It appears they are all vintage glazed ceramic from Japan.