Hey,
Fantastic job. Just take care about categorizing the images properly. To avoid confusion and complexities create one unique category like WP takes Kolkata.
After photographing are you going to gather once again and upload the images at same time or individuals would later do it on their own?
Also I guess Ahswin is there in Kolkata, please do get in touch with him and try to get the list of Images needed for Kolkata related articles.
And one more thing, who all are going to participate? Wikimedia Contributors or newbies?
If you need any help please do not hesitate to get in touch with me over this thread or off list. Thanks.