Derek Medina admitted taking the picture on his phone and uploading it on to the social media site.
He failed to convince the jury that he had shot Jennifer Alfonso eight times in self-defence after years of abuse.
He said his wife was threatening him with a knife when he shot her in their home in Miami, but prosecutors said she was cowering on the floor.
When he posted the picture, he wrote on Facebook that he expected to go to prison or be sentenced to death for the killing.
Prosecutors successfully argued that the 27-year-old wife was in fear of her life when she was shot in August 2013.
Medina had vowed to kill her if she left him and she had told friends she intended to do that, the court heard.
Miami-Dade State Attorney Katherine Rundle said: "No family should ever have to see their daughter killed and then exhibited worldwide on the internet like some macabre trophy to a husband's anger."
Medina, 33, faces a sentence of 25 years to life for second-degree murder.

Watson, world ranked 110th, was beaten 7-6 (7-2) 6-2 by the Estonian Anett Kontaveit, who is the world number 99.
The 24-year-old faced 18 break points - compared to just one for her opponent - on the way to losing.
World 124 Broady was beaten 6-4 6-2 by German Julia Goerges, who is 46 in the women's rankings.

Ricciardo and Vettel are respectively 60 and 117 points behind leader Lewis Hamilton with 150 still available.
Red Bull team principal Christian Horner said their title hopes were a "long shot" but Mercedes' reliability problems gave them a chance.
"Due to their shocking reliability, hopefully we can keep ourselves in the championship," he said.
Although reigning champion Vettel is almost completely out of the reckoning and has only a mathematical chance, Horner says it is too early for Red Bull to consider team orders to aid Ricciardo's challenge.
Vettel finished second to Hamilton in Singapore on Sunday with Ricciardo third while Nico Rosberg retired with an electrical failure.
"Mercedes have an enormous advantage at this point," Horner said. "We'll take it one race at a time. Both of them are still just in it and both have taken a chunk of points out of Nico.
"Daniel, OK he's conceded three points to Seb but is that going to make the difference? Impossible to say with a crystal ball at this stage but at the moment it doesn't make sense to interfere with team orders.
"Daniel is totally comfortable and happy with that.
"If there was a realistic chance of Daniel winning and Sebastian was mathematically out of the championship, then we'd do the best we can for the team but the situation we're in at the moment is it's a long shot."
A Florida man who killed his wife and posted a photo of the body on Facebook has been found guilty of murder.
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British pair Heather Watson and Naomi Broady were both knocked out in the first round of the Biel Bienne Open in Switzerland.
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Red Bull insist Daniel Ricciardo and Sebastian Vettel are still in the fight for the drivers' championship.