Any customer who wants to know who makes the mozzarella in Greg Tosto's Greenwich Village deli need search no further than Tosto's business card.

The wallet-sized handout is a snapshot, a one-frame documentary. It shows an aproned Tosto "stretching" mozzarella with a paddle, the final act in the preparation of the chewy white Italian cheese.

Superimposed on the picture are the words "Pasta Villaggio, Home of the Freshest Mozzarella" as well as such information as the location and phone number of the deli and the names of its owners, Tosto and his brother, Fiore.

"The card is very effective," Tosto said. "It shows ... that's what I do here: I make mozzarella... . The picture is worth a thousand words."

Though some button-down etiquette mavens may preach understatement in corporate protocol, colorful and sometimes flamboyant "photo business cards" are making headway in a world once ruled by staid white paper and black lettering.

Photo business cards were rare five years ago but today constitute roughly a $10 million annual business, said Edward Zito, president of Positive Concepts Ltd., an Atlanta photo-card manufacturer.

They are, however, more expensive than their no-frill counterparts. The glossy cards range from $135 to $375 per thousand, while the plain paper versions start at about $25 per thousand.

Nonetheless, the small businesses that are the main customers of photo cards are willing to pay such prices because they see the cards as an eye-catching way to leave a phone number with a potential client.

"It's been my main marketing tool," said Bilal Muhammad, owner of Bijaan Limousine Ltd. in Brooklyn.

Muhammad's card, which is given to maitre d's, concierges and such other business contacts as hotel, restaurant and airport employees, shows a gleaming silver Rolls-Royce, the automobile used by Bijaan patrons.

In front of it stands Muhammad, dressed in a gray suit, striped tie, chauffeur's cap and white gloves. In the background is the Manhattan skyline.

Muhammad uses the card to impress potential customers who want to know what their driver and car will look like.

"Everyone comments on it," said Muhammad. "I think it's kept me in the mind of a lot of people."

Other businesses have slightly different reasons for using the cards: Eli Blick, owner of Rely on Eli in Queens Village, N.Y., uses them to gain the trust of would-be clients. Blick is a home remodeler and "you now how people are when it comes to contractors: 'Who will I have in my house?' " He believes a business card that shows his face helps reassure homeowners. D. Jay Gregg and Co., a West Hempstead, N.Y., business that provides disc jockeys for parties, uses the cards to emphasize that Gregg employees dress well. The Gregg card shows them clad in black tie. "It tells all," said Nina D'Agostino, partner with her husband in the company.

Don Arbital, a broker who sells investments such as penny stocks and mutual funds over the telephone for Investors Center Inc. in Melville, N.Y., said the cards are a way to establish a relationship with people who know him only by voice.

After he makes a call to a potential client, Arbital sends a follow-up letter with his photo business card attached.

"I've sold stock to people who said ... I'm looking at your picture and writing out a check to send to your company," Arbital said.

The cards have generated an unexpected return as well: Arbital has gone on six dates with women who read his note, saw the attached photograph and called to ask him out. "It's hysterical," he said. "They've taken me all kinds of places. I saw 'Cats.' "

Such praise is music to the ears of the card vendors, members of a young trade hankering after some of the hundreds of millions of dollars Americans spend annually on business cards.

Nationally, vendors include a small crop of quick photo shops.

The trade is dominated by a handful of national companies that manufacture the cards and market them in a franchise-type network of local distributors.

The oldest and biggest of the companies is Positive Concepts, begun five years ago by Zito. He is not quite sure who first came up with the idea of replacing plain paper with photographic paper, but, like many in the industry, he guesses it was Eastman Kodak, which for some time has manufactured photo business cards for its employees.

Positive Concepts tallied sales of about $3 million last year, largely through the manufacture of about 24 million photo business cards sold under the trade name of Trump Card.

Competing cards, called Ad Shots, are made by The Visual Advantage Inc., a Roanoke, Va., company founded by former Positive Concepts distributor Dale Turner. He expects Advantage, which also markets "s-mug shots" -- business cards for high school seniors -- to be churning out about a million cards monthly by this summer.

Colorfast Marketing Systems Inc. of Chadsworth, Calif., meanwhile, is just beginning to expand its PromoKard operations to the East Coast and currently produces about 250,000 cards a month, said Keith Phillips, vice president of sales and marketing for the 2-year-old company.

George Srolovits is one of the five active Positive Concepts distributors in the New York area. Like many Positive Concepts affiliates, he saw an ad for the company in Entrepreneur magazine and then paid $6,000 to $7,000 to buy a distributorship.

The fee entitled him to camera equipment and other supplies to set up shop, as well as a five-day training course in Atlanta.

"They told me I talk too fast; I said, 'I can't help it, I'm a New Yorker,' " he said.

Srolovits likes to explain the idea of photo business cards with his motto: "You never get a second chance to make a good first impression."

For not quite two years, he has run his business, which he calls Creative Business Images, from an immaculate basement home office, equipped with a computer and a Yashica-topped tripod.

After working out with a customer the right look for a card, Srolovits takes the picture himself or hires a photographer. He then ships the proofs of the card to Positive Concepts, which manufactures the final product.

Srolovits said his several hundred clients come from a variety of backgrounds.

Among them are insurance agents, dentists and a smiling urologist whose card shows him with a stethoscope peeping out of his white jacket pocket.

But other card sellers specialize in pitching their wares to particular trades.

Arthur Messina, a 25-year-old former nightclub manager and hobbyist photographer who "had the desire to do something for myself," spends a lot of time at limousine trade shows, selling cards to limo-fleet personnel.

Messina, who sells cards outside the limo industry as well, has been running Create-A-Card from his West Babylon, N.Y., home since September 1986.

All the vendors say they have learned a thing or two about art and composition since taking on photo cards.

Messina likes using local sites as backdrops for his work.

Srolovits discourages his clients from posing while holding a telephone, because "it's a little too hokey" and encourages them to put on a smile that makes them look "relaxed, self-confident, professional."

He is particularly proud of a project under way now.

The client owns a tile-cleaning business. The challenge is how to demonstrate her trade in a 2-inch-by-3 1/2-inch photo card.

"She has these blue overalls and this cap," Srolovits said, "and she'll be holding two tiles, one 'before,' one 'after.' "