Can I drive a rental12-seater vehicle in New York on a European B drivers licence?

Your B license is in the same category as the US standard license, an unrestricted license which allows you to drive passenger vehicles for your personal use (and that of your family/group). In both, there are other licences for those who chauffeur (taxi, limo, etc.), motorcycle, and commercial (heavy trucks and buses, and the like).

As long as you meet the rental company rental conditions for a 12-passenger van, there shouldn't be a problem. A quick look at several (National, Enterprise) suggests that there some common terms for a vehicle of that size, the basic ones being that the driver has to be a minimum of 25 years of age and has appropriate insurance coverage.

Here are those excerpted from National's additional requirements for 12- and 15-passenger vans:

Renters of these vehicles must be 25 years of age or older. If the primary driver of this vehicle is 25 years of age or older, they must accept the terms and conditions below.The following terms apply to the rental of this type of vehicle, in addition to those set forth in the Rental Agreement.

The van will not be operated or used in Canada.

The van does not meet Federal Bus Safety Standards and will not be used to transport children in the twelfth (12th) grade or younger, other than family members, for school related functions.

All renters and additional drivers must have liability insurance that transfers to the rental vehicle. For a personal auto policy the renter and all drivers must have minimum liability coverage of $100/$300k or $300k combined single limit.

To expand, after some discussion with @phoog, to whom thanks, and additional searching, this New York State Department of Motor Vehicles Driver License Class Descriptions should make it easier for you to make a comparison.

Coincidentally, a Lonely Planet question addresses the very same topic:

marcin_niedziolka asked:

Will my IDP (International Driving Permit from Poland) plus my Polish driving license (I have category B) will be valid for driving a van (12 passenger) in USA? I want to rent a van [in] NYC and drive around country.

bzookaj replied:

In the US, if you can rent a car, you can generally rent a 12 person van. They are not split like they are in Europe.

In New York, specifically, the "class B" is for large trucks, those over 26000 pounds (roughly 11800 kg), which are not for towing large loads (i.e. not tractor trailers, etc.). The class D covers personal vehicles and vans, so is roughly equivalent to a combination of the European class B and D.

marcin_niedziolka responded:

[That's] the same answer I got from DMV NYS just few minutes ago: "As long as the van is not over 26,000 pounds, your international permit and Polish license is valid to drive it." In Poland "class B" only allows you to drive minivans up to 9 passangers (including driver).

Update: apparently, the interpretation outlined below is not shared by the New York State Department of Vehicles. Over at lonelyplanet.com, you can find the following reply to the same question:

The same answer I got from DMV NYS just few minutes ago: "As long as the Van is not over 26,000 lbs your international permit and Polish license is valid to drive it."

In addition to this, however, I note for other readers that vehicles carrying 15 or more passengers in addition to the driver are, in New York State, at least, defined as commercial vehicles, so someone with a class D license from New York (or the equivalent from another jurisdiction) is not authorized to drive such a vehicle regardless of its weight rating. See http://codes.findlaw.com/ny/vehicle-and-traffic-law/vat-sect-501-a.html.

Here is my original, apparently incorrect, analysis:

It's not exactly explicit, but I believe that the New York law requires you to comply with the terms of your license. Here's part of the relevant subsection of the Vehicle and Traffic law, §250, Exemption of non-resident owners and operators:

2.?A person of the age of sixteen years and upwards who shall be a nonresident of this state, and a resident of a state, territory, federal district or foreign country having laws, with which such person has complied, which require such person, in order to operate a motor vehicle or motorcycle therein, to be licensed, may operate or drive a motor vehicle or motorcycle on the public highways of this state without being so licensed under this chapter, ...

The key is "with which such person has complied." If you operate a vehicle that your license doesn't allow you to operate, you are presumably not in compliace with the laws of your licensing jurisdiction.

Having said that, the rental company, and even a police officer in a traffic stop, is unlikely to notice. Just don't let it come to an insurance claim.