Myuran Sukumaran and Andrew Chan have been told they may be executed as soon as Tuesday.
The pair was given notice on Saturday of Indonesia's intention to execute them in a minimum of 72 hours, during a meeting on Nusakambangan Island.
Lawyer Julian McMahon returned with three self-portraits by Sukumaran.
One canvas was dated April 25 and signed "72 hours just started".
Foreign Minister Julie Bishop said the thoughts and prayers of many Australians were with Chan and Sukumaran.
"I spoke to Mr Sukumaran's mother Raji yesterday and assured her the government would continue to seek clemency from Indonesian President Widodo for both men," she said in a statement.
"They have been rehabilitated in a most remarkable way over the past 10 years and are genuinely remorseful for their serious crimes.
"Nothing can be gained and much will be lost if these two young Australians are executed."
Ms Bishop also urged for Indonesia to respect legal challenges before the Constitutional Court and Judicial Commission, which she said raised fundamental questions about the integrity of the sentencing and the clemency process.
"I again respectfully call on the President of Indonesia to reconsider his refusal to grant clemency," she said.
"It is not too late for a change of heart."
Jakarta had pledged to wait for all 10 prisoners in line for the firing squad to exhaust their legal avenues before naming what the attorney-general's spokesman Tony Spontana termed "D-day".
Indonesian Zainal Abidin's bid for a judicial review is expected to be determined on Monday, and lawyers for Filipina Mary Jane Veloso submitted a new judicial review request on Friday.
Regardless, Veloso was told the executions would be held on Tuesday, news website Rappler reported.
Prime Minister Tony Abbott is set to discuss the executions with French leader Francois Hollande on Monday.
France managed to win a reprieve for its death row citizen Serge Atlaoui, Fairfax Media reported.
Also making an appeal for mercy on Saturday was Sukumaran's sister Brintha, who released a brief YouTube video.
Clutching a photo of her big brother as a child she said: "From the bottom of my heart please President Widodo have mercy on my brother."
The Chan and Sukumaran families were making their way to Indonesia on Saturday.
Mr McMahon did not comment to reporters but showed Sukumaran's self-portraits, the others signed "Our new prison. A Bad Sleep Last Night" dated April 25 and "A strange day" dated April 24.
Sukumaran, 34, attained a degree in fine arts while in prison in Bali, where he and Chan, 31, were model prisoners and leaders in rehabilitation programs for fellow inmates.
They were arrested 10 years ago in a foiled bid to smuggle heroin out of Indonesia.
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