50 Cent jacked a couple photos & plastered them on his social media to pimp himself & one of his products ... so says a photographer in a new suit.

Christopher Pasatieri - who says he's a professional photographer - says he photographed 50 Cent & some of his shots ended up on the rapper's IG page, each generating more than 42,000 likes.

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In docs, obtained by TMZ, Pasatieri submitted a screen shot of the Instagram posts that shows Fiddy pimping his SMS Audio headphones & TV show, "Power.

Pasatieri says the rapper never licensed the photos or asked for permission to post them on Instagram. Pasatieri doesn't say when he shot 50 but it seems it's from a concert back in June 2014 at Citi Field where he performed with G-Unit, which is also being sued.