Good work there. You got the body assembly stored in perfectly. To make it appear more gundam like, add the eyes in and make it's shape pentagon shaped. So it's the same as you put a rectangle then an upside down triagle under it. Add robotic looking ears to it by making it squarish looking on each side of the face. And you could add a wing on it's forehead like most gundams. Feel free to select the size and shape of the parts. I hope these help. If you need more mecha reference, it's best to get the HTDM giant robots book. I've learned how to draw mecha from that.
Take note of using color. You should vary the shades' hues. When varing hues, stick to the low saturated colors. These lead to hue varations which can break up the monotony in your images.
