This artist
https://www.artstation.com/nivanhchantharais very cool, I used his art a few times. Scroll down for some urban / favela looking future soldier stuff.
Other visual references you obviously could use are the futuristic Call of Duty games concept art, the Killzone series, Halo, some Tom Clancy Splinter cell ghost recon rainbow six near future stuff etc, etc. Search for those concept artworks on artstation, there is a lot of unused content usually cut from the final games
