Are any additional margin/ brokerage charges imposed in case I want to take delivery of commodity ?
You can give/take delivery on commodity contracts which have physical settlement. If you intend to give/take delivery, you need to let the broker know about the same during the delivery period (which will be mentioned in the contract specification).
As soon as you do this, there is an additional margin of 25% and yeah the brokerages in case of physical delivery will be much higher and vary from broker to broker. Note that most online brokerages, don't allow you to take/give physical delivery and usually will ask you to close out all positions before the contract gets into compulsory delivery period.
Delivery (give/take) can be effected only in Exchange accredited or designated warehouses. You can find this list on the exchange website.
You can read this document for all FAQ's on delivery, and also make sure to look at contract specification for every commodity, usually everything would be mentioned on that.