it depends if you seel it to the right demographic and if you have proof of authenticity. people would be very hard pressed to buy just a photo. you would need something to say it actually is what you say it is. or you might find some dummy on ebay to but it.
An original 1962 Marilyn Monroe picture can be worth between $20 and $50 depending on its quality. You can get a proper price quotation for the picture by scan the photo and sending it to an appraiser.