I'm involved in our internship program at my company, as mentioned above, would accept whatever they offer.
There's probably a list of people they turned down just to get to this point, they can always call the next person on the list.
The one place I would say there is some wiggle room, is "living allowance". We pay the same rate to all interns, but if someone is put somewhere abnormal for their internship, or doesn't have family in the town of the office they are going to, we give varying amount of living allowance $ above the standArd salary.
Also mentioned above, internships are a test drive for the company, they get to see work ethic / problem solving / multitasking/ social skills for an extended period of time. The company (should) spends a lot of money and time on interns, hoping it works out and they find a good permanent employee. Don't ruin it right out of the gate "negotiating" salary. Everyone in the company will know, and it will follow you. It will give everyone a pre-conceived notion of entitlement, an issue/image that the current generation doesn't need any help creating.