Wih so few pixels, it's better to convey the object and not the detail. There is no space for small details. That and the colours you're using lack contrast to even suggest a change in surface. 

I would agree, but I find that the magic in small size pixel art is trying to convey as much detail as possible with such a small amount of pixels, which is what I tried, however it is incredibly tough for i.e. robes.

At this size, I'm not entirely sure I'd even try and detail a robe. Just keep it simple.