Well, there should be some warm colors at front if there are some cold ones at back, for the purpose of contrast. Also, those blue flags look really flat and distracting.
One color cannot result a dynamic coloring. As you can see, there is transitions of colors in my example, so we don't have just one color. At back, soft transition from purple to blue types; at front, "purple to red, red to orange, orange to yellow" types. It is a game of temperature.
This result would also look good in the icon size, because there is a pure definition defined by a good coloring and lighting.
But these are not really necessary in this case, because you've these already approved. These are just some personal points that could perhaps be some motivation for the next works, as practice makes perfect! :]