The entire remodeling of this section of the palace was designed by Roman Meltzer, who also had done the remodeling of 1895 in the AP. Ernst-Ludwig's involvement was in the arrangement of the furniture, discussions about the overall design, the colors, fabrics, etc. He rearranged the furniture in Alix's Reception Room as well.
In coming up with the designs of the New Study and the Maple Room, Alix wanted something very modern, comfortable in the Darmstadt style. You can see some of things going on in the Artist's Colony in residential interior design for some comparisons - obviously on not such a grand scale.
Meltzer's furniture in particular shows the impact of work by Darmstadt artists and Architects like Peter Behrens. You might even call them knock-offs.
Bob