The designs focused on a range of subjects including the fossil fuel industry, the bravery of the local firefighters and the destruction of the country's flora and fauna.
Well-known street artist Scott Marsh contributed an image of Prime Minister Scott Morrison emblazoned with the words "climate denial".
One of the co-organisers, who asked to remain anonymous, told SBS News the idea started on an Instagram group message.
"There was this universal feeling of powerlessness and helplessness amongst all the artists."
She said the artists were particularly concerned "how things were being handled over the past couple of months by the government".
"The act of taking over the advertising spaces is a symbolic thing, it's the narrative of taking back public space or space in the media that we felt wasn't being given to these issues."
"In conversations with the artists, I don't think there's anyone that hasn't been personally affected by the bushfires this year, or they have had a family member who was affected."
Each artwork also features a call to action and a QR code to a charity of the artist's choosing.
"There's everything from fire relief for First Nations communities to water conservation to the Climate Council," the co-organiser said.
Over the course of the bushfire season, 33 people have died, thousands of homes have been destroyed and more than one billion animals have been killed.