NEW YORK >> At twilight Monday, something new will light up a Times Square billboard. An original work of art, 23 stories high, will replace a bright yellow ad for Sprint.

The artist whose work now gets a canvas that Rembrandt could never have imagined is a substitute teacher from Allentown, Pa., who has made art for more than 30 years but never had the backing of a major museum or gallery. Her creation will loom over Times Square because she won an online contest in which users of a website gave her more votes than 35,000 competitors.

The site, ArtistsWanted.org, is not a charity but a business, one that hopes to make a profit identifying artistic talent and connecting it to an audience. Investors are pouring millions into it and similar startups and social networks like Behance.net and EveryArt.com, which cater to the growing cadre of people who consider themselves creative and think there is a market for their work outside the network of galleries and dealers who dominate the commerce in art and design. Users and founders of these sites talk not only about making money but also about democratizing culture.

As these platforms proliferate, they also raise questions about the nature of art and creativity, the distinction between professionals and hobbyists and what it means to call yourself an artist when anyone with a cellphone can be a photographer, anyone with the right apps can be a designer, anyone with a Facebook page can amass a following, and anyone can dream up a concept and find a place to pitch it.

“The value of the creative industry, the value of creative talent, has become more appreciated over the past few years,” said Mukti Khaire, an associate professor at Harvard Business School.

“The fact that the Web creates opportunities for discovery and showing that nothing else could on that scale — I think it does change who gets to be an artist,” added Khaire, who studies the creative fields. “It may not change the definition, but it widens the funnel.”

William Etundi Jr., a founder and chief executive of Artists Wanted, is banking on that mass tech-enabled populace.

“As technology has made it easier for people to create things, more people become creators,” he said, offering a sort of company motto.

He started the site four years ago, with Jason Goodman, a founder of Third Ward, an art and design collective in Brooklyn, where Etundi, 33, planned events. They hosted artist calls and competitions, partnering with other businesses. As 60,000 users registered and remained engaged, Etundi sensed a larger opportunity. In February they raised $1.5 million from investors including OATV, which backed bit.ly and Foursquare, and Founder Collective, which invested in Art.sy and Vimeo.

The ethos, Etundi said, “is to inspire creative people to make works they wouldn’t otherwise create, to give them an audience, to give them connection, to give them deadlines within competitions.”

In its venture-financed expansion, Artists Wanted, which now has a staff of 14, plans to run four competitions a year, letting the site’s community pick the best contenders in art, photography, fashion and more but retaining the right to name the winner (as it did for Times Square). Its business plan is a mix of free and paid services, allowing users to post their work free but charging for deeper usage — $25 to get your portfolio on the home page during a contest, say, or perks like after-party tickets. Its visitors quintupled from 41,000 in January to 208,000 in April, according to Nielsen, and it already has revenue — $1.3 million last year, although it is not yet profitable, Etundi said.

Artists Wanted also has deep cultural connections. For its event Monday in Times Square, Etundi enlisted Questlove, the drummer from the Roots, to host, from the pedestrian plaza on 43rd Street, and to DJ the after-party nearby. Through Chashama, the arts nonprofit founded by Anita Durst — a scion of the Durst Organization, the developer that controls some Times Square real estate — he got access to three major digital billboards (on the Nasdaq, Thomson Reuters and Port Authority buildings). The Times Square Alliance, which also had ties to Durst, donated space on a dozen more, for a month.

Also thanks to Durst and the real estate firm Rockrose, Etundi has a 4,800-square-foot office space in Queens — complete with a gallery for his site’s artists — rent free for a year, with subsidized rates to follow.

“I believe Will — his philosophies — they help build the arts community in New York,” said Durst, who met him a decade ago, when she frequented his loft parties. “He really cares in a very heartfelt way.”

Artists Wanted is entering a competitive field. DeviantArt, the most popular art and graphics website, according to Nielsen, has 19 million members, many with a techno aesthetic. DIYers have Etsy; photographers have Flickr; everyone else has Pinterest and Tumblr.

Last month Behance.net, which bills itself as a platform for creative professionals, announced its first round of outside financing, $6.5 million led by Union Square Ventures. One million new works went online in the past six months, as many as in the company’s first four years, said Scott Belsky, a Behance founder. Emboldened by handy technology like the photo app Instagram, amateur users are scaling up, he said, while professionals, mindful of new competition, are broadening their skills.

Albert Wenger, a partner in Union Square Ventures, said these new sites represent a changing understanding of the artistic economy.

“What the Internet does is turn hobbies into things that are, in some instances, a global opportunity,” he said.

The fine-art world has also recently made forays online, with sites like Art.sy, an art recommendation engine; Pictify, which allows users to post and “collect” images of Van Goghs and Monets; and EveryArt, where patrons commission artists.

With this avalanche of new creativity online, Jeffrey Deitch, the director of the Museum of Contemporary Art in Los Angeles, argues that “there is an increasing need for curators and connoisseurs to make sense of it for people.”

“I have not yet heard of an artist, like a painter or sculptor, in the mainstream of art becoming an Internet sensation,” he added. “It’s not like Lana Del Ray, where a giant music star starts on the Internet.”

But he said the path for such a breakthrough was clearer for a conceptual or video artist.

For Vicki DaSilva, 52, the winner of the Artists Wanted “Art Takes Times Square” contest, the Internet has been her gateway. She first noticed an uptick of attention in 2009, after she started posting videos of her work, known as light graffiti, on YouTube. She was attracted to Artists Wanted because of “their mission,” she said, to give exposure to artists who were out of the mainstream.

“I feel like this is the perfect place for me,” she said.

Her winning entry, a multimedia piece with the words “never sorry” written in homage to Chinese artist and dissident Ai Weiwei, earned her $10,000.

The money was appreciated, DaSilva said. But she was beyond thrilled at the prospect of seeing her work 23 stories tall on a city billboard.

“This is my Frank Sinatra, Jay-Z moment, my ‘New York, New York’ moment,” she said. “You can’t get bigger than Times Square.”