London, England (CNN) -- This year's shortlist for the prestigious fourth plinth commission in London's Trafalgar Square is the most international yet, with artists from Germany, the U.S., Puerto Rico, Denmark, Norway and the UK in the running.
Proposals include a giant blue cockerel by Katharina Fritsch, an oversized sponge cake made of bricks by Brian Griffiths and an ATM machine whose buttons can be pressed to play an enormous pipe organ, designed by Allora & Calzadilla.
Ekow Eshun, chair of the Fourth Plinth Commissioning Group, told CNN: "There's been a real shift in the last few years from it being chiefly British artists showing, to international artists of real caliber wanting to take part.
"Particularly this year, artists from all around the world seem really motivated to propose concepts for the plinth, with a strength and ambition that we haven't seen before."
Since 1999, artists have vied for the chance to temporarily fill the plinth -- left empty for more than 150 years after the original statue was never completed -- with winners chosen by a panel of leading curators and artists, following feedback from the public.
Controversial choices such as Marc Quinn's 2005 statue of a naked, pregnant, disabled woman have helped turn the competition into a subject of feverish debate, and the plinth has grown to become one of the hottest contemporary art commissions in the world.
Paul Hedge, director of London's Hales Gallery -- which has sold the work of plinth-shortlisted artists -- told CNN: "All the artists I know would give their eye teeth to exhibit on the plinth. Apart from anything else, the footfall in Trafalgar Square, with millions of people from all around the world passing through it, is enormous. Just being on the shortlist can boost the price of an artist's work.
"But what's special about the commission is that it's about artists talking directly to the public -- it's not an experience mediated through a gallery. It has challenged the notion that contemporary art doesn't have anything to do with ordinary people's lives."
Ordinary people even became the art last year, in Antony Gormley's offering "One and Other" -- which saw 2,400 members of the public get the chance to spend an hour each on the plinth. They used the time to do everything from getting naked to dressing as Godzilla.
"Most public art has a lot of constraints on it, which is why it's often so terrible. But when you make something for the fourth plinth, you get the kind of freedom you'd normally only have if you were working for a gallery -- which is exciting," said Hedge.
Exciting it may be, but jostling for attention with neighboring landmarks such as Nelson's Column can also be daunting for the aspiring fourth-plinther. British-Nigerian artist Yinka Shonibare, whose work currently occupies the coveted position, tackled this challenge head on by stuffing a model of Nelson's ship into a bottle and dressing it with colourful textiles that hint at Britain's colonial past.
Hew Locke, a Scottish-born artist who grew up in Guyana, is one of the six shortlisted to take over the plinth in 2012. He told CNN: "Creating something that works in a public arena is tricky. I spent night after night wandering around Trafalgar Square, looking up at the plinth and thinking, 'What could I put up there?' I wanted it to be something that combined the traditional and the contemporary."
His proposal, entitled "Sikandar" -- the Urdu name for Alexander the Great -- examines themes of heroism and veneration. It turns a replica of an equestrian statue of Field Marshal Sir George White -- a hero of the Second Anglo-Afghan War in the 19th century -- into a fetish object, decorated with charms, jewels, medals and masks.
If it wins, it will only have the chance to take to the plinth for 18 months, before it is replaced.
"I don't mind -- the fact that the statues keep changing means that, unlike the other plinths in the square, the fourth plinth stays alive." Locke said. "For me, it means it becomes a beautiful memory."