Nudibranch stamp series designed by Simone Sakinofsky at Australia Post. Kretschmar was thrilled to be asked, but also realistic. She knew it would be a long process involving many critiques and committees before final approval. She had friends whose designs had been archived without being released. She was given the choice between designing separate stamps or a mini-sheet, with stamps cropped from a larger scene; she went for the mini-sheet. The basic rules: each stamp must bear the word "Australia" and the price (the year of issue also appears in micro-type); and the design must include light areas for Australia Post's letter sorting machinery to recognise the stamp. The traditional Christmas stamp has extra rules such as Mary's garb (it must be blue) and a halo for Jesus (compulsory). Above all, it must be respectful. The most controversial stamp was the Surfing Santa of 1977. Australia Post received a huge backlash with complainants saying it did not treat Christmas seriously. The postal service had started producing a mix of secular and religious Christmas stamps just a year earlier. When the Surfing Santa was re-released in 2007 as part of a 50 years of Christmas Stamps issue, there were no complaints.

Sonia Kretschmar with her Christmas stamp design for Australia Post. Credit:Sonia Kretschmar Kretschmar's design got through with relative ease. There were a few tweaks – the animals' expressions, the exact blue of Mary's dress – but the query she expected, about her golden Madonna, was never raised. "I wanted to make her skin tone a bit ambiguous, so she's not traditionally like a white Mary, she could be any colour," says Kretschmar. The duck, a small tribute to Melbourne cartoonist Michael Leunig, didn't make it into the stamp crop as it was considered too non-traditional. The stamp business, and stamp collectors, tend to be conservative, says Australia Post's philatelic manager Michael Zsolt. "We see stamps as a record of Australian history, it's a very important part of our role and we take it very seriously," he says. "So we're not in it to make political statements or take sides on any issue." Sonia Kretschmar's traditional Christmas 65 cent stamp design for 2015. Before 1997, no living person apart from the monarch and her family was allowed to appear on Australian stamps. Since then, they have featured Olympic gold medallists, Indigenous leaders and the Living Legends series, which began with Donald Bradman and has included medical scientists, writers, philanthropists, cooks and Australian music legends. This year, it was recipients of the Victoria Cross.

To select the legends and make sure each design is accurate, the philatelic team has three inhouse researchers and consults with experts and cultural bodies, though sometimes this advice is queried by zealous collectors and interest groups. The controversial Surfing Santa stamp of 1977, re-released in 2007 by Australia Post. "It can be as simple as putting black colouring on a wasp in slightly the wrong spot," says Zsolt. Last year's Things that Sting children's issue included a European wasp, but its colouring raised conjecture. Experts maintained it was right, but "there's still a bit of to-ing and fro-ing", Zsolt says. The design team does get to have some fun. Another children's issue had glow-in-the-dark ink, with hidden fossils only visible under UV light. Australian children's author and illustrator Graeme Base hid insects in his stamps. This year's Centenary of WWI: Gallipoli stamp issue includes a limited edition mini-sheet incorporating shavings from the Australian War Memorial's Lone Pine tree as part of the printing process, an Australian first. Simone Sakinofsky​ has worked at Australia Post's design studio for nine years. Asked to nominate some of her favourite stamps, she includes a series of nudibranchs, tiny colourful sea creatures she had never heard of before taking on the project. Rather than using plain photos, she designed an underwater landscape for them to float in, with waves and sand and tiny bubbles when you look closely.

Stamps usually have a level of detail most people will never notice, but nothing gets past the collectors; the designers often work with them in mind. "They get out their eye pieces and magnifying glasses and look for the hidden detail," Sakinofsky says. "They'll let us know what they think and what they've found." When creating a stamp, Sakinofsky works at 400 per cent of the actual size. "With stamp design you're learning to communicate on a very, very small platform and there's lot to say," she says. What works at 400 per cent doesn't always work at 100 per cent. "You're always trying to simplify and think of different ways to get your message across." It's still a thrill to see her work outside the office. "Sometimes you open the mailbox and say, 'Oh, I designed that!' Or someone will send you an invitation with your stamp on it." As for Kretschmar's debut stamp, the illustrator confesses she doesn't usually send Christmas cards. "But I guess this year I'll have to."