An observation: the chandelier in the dark room doesn’t work with the sputnik one.

Something like this light would work. Rectangular in shape, so great for over the table, and the same metal as the sputnik.

Assuming the dark room is the dining room, then bring that color into the living room with a sofa in that color.

Art can be whatever you love, and considering It is a playroom, something fun would be appropriate.