Looking at these photos again, I realize whoever did them really spoke volumes with how the characters are postured, posed, and placed (unintentional alliteration there).
Jack is sitting in the center, and he’s above everyone else. Ianto and Gwen are sitting at his feet, saying that he’s the leader and that he has to be the one to save them and protect them. And look at that fearlessness in his face, but you can tell he’s scared as well because he’s not smiling. The Jack that knows he’s gonna win would smirk. But this Jack is sitting there with a slightly creased brow and an almost-frown. He’s scared. He’s unsure.
Ianto and Gwen are sitting below him, signifying their reliance on him to be the leader and how they look up to him for support and guidance. Gwen is sitting near Jack, but she seems oddly detached. She’s looking away and her hands are clasped, to herself. She’s leaning on Jack, counting on him, but she’s already dreaming of that life out on her own and a family she now has to protect, or maybe even something else. And you can just see Jack sitting there, with one hand on her arm, keeping her there, keeping her from running away because he can’t live without her. He’s already lost everyone else. He needs her like someone who can’t bare to lose another friend. I think if the hand were meant to symbolize him keeping her in check, it would be on her shoulder. The way Jack is reaching down to grab her makes it seem like he’s trying to keep her from running away.
And Ianto. His body language echoes support because he’s actually touching Jack. Ianto’s hand is on Jack’s knee, saying that he supports Jack and that he’s there for him. The way he’s looking down with his eyes closed seems to say that he’s putting faith in Jack. Eyes are important, vision is important. Gwen is looking elsewhere, signifying her detachment from Torchwood, and Ianto has his eyes closed, putting him in a vulnerable position and his life in Jack’s hand (but let’s not go there). Ianto’s hand also shows reassurance, him reassuring Jack that he’s there and that he’ll be there to protect Jack too. It also shows how Ianto keeps Jack grounded and as close to whole as Jack can get at this point.
And finally, one more big thing on Jack’s body language. You can very clearly tell that he is leaning toward Ianto. His leg sticks out a bit on Gwen’s side, almost as if keeping her at a distance. He loves her (like a friend) and doesn’t want to let her go, but he also doesn’t feel the same way about her as he does with Ianto. He’s close to Ianto, leaning toward him for support. This posturing also shows their relationship and how Ianto is probably much closer to Jack than Gwen is.