In terms of the halachos in Shulchan Aruch Orach Chaim Siman 85 (which places is it ossur to say Krias Shema) would a small room with just a shower head have the same dinim as a room with a toilet or a room with just a bathtub?
Did you also see Siman 84? It talks about a Bathhouse, which is what a room with just a shower or tub is.
However, a modern bathroom, where everything is flushed away probably also has the din of a bathhouse.
Siman 85 applies where the waste is actually present.