Hi Suman, little surface details like that tend to be better put on as texture maps in a rendering program rather than directly modeled.

Also it tends to be difficult to model things like that in a CAD program which is based on structured object and profile curves. If you did want to model it I'd recommend using a displacement sculpting program such as ZBrush or 3D Coat, they are more oriented around those kinds of bumpy details. MoI itself is not focused on that type of modeling.

- Michael