The jihadists pose with air rifles and alongside a fighter jet
Rumaysah, real name Siddartha Dhar, fled the country to join the Islamist militants with his pregnant wife and four young children in September.
The jihadist had been arrested by counter-terrorism police during a series of London raids.
The former Hindu previously posted a picture of himself holding an assault rifle in one hand and his newborn baby in the other while in the war-torn country, before his Twitter account was suspended.
It is only the second photograph of Rumaysah to emerge since he joined the terror group and was uploaded by Britani.
The post on Twitter
Maybe next time myself n Abu Rumaysah r 2gether it will be head of nusayri uk usa french jordan Saudi pilots head. (sic)
He added: “Oh pilots of the coalition! We will down you, we will hunt you down & we will kill you”.
Rumaysah is associated with radical preacher Anjem Choudhary, who was also arrested during the operation last year.
The jihadist was supposed to hand over his passport after being granted bail but fled London by coach.
A Metropolitan Police spokesman said: “Abu Rahin Aziz remains wanted by police having been found guilty of the offences as charged in their absence from court.
“We would not wish to speculate on where they are at this time.”
The pair are among an estimated 500 Britons believed to have fled to Syria to join the Islamic State, who have captured large swathes of the Middle East over the last year.
This week, British terror police revealed that a suspected terrorist is arrested everyday in the country in connection with Islamism extremism.
The latest figures show the number of people arrested for terrorism charges has risen by a third since 2013, to a total of 327.
Some 165 people were arrested in relation to Syria, which shows a major increase from 25 in 2013.