First of all, this is amazing and powerful. I want to shed tears for Legion and Tali and I've only looked at it for a few seconds. I feel that the "Halo" vibe you mentioned is a little apparent, but it's a good addition. Halo does a fantastic job about making you want to cry for the characters and the trauma they endure, and this picture needed that somber tone. I really love this picture, and it's really interesting that I was just thinking about writing a fic where this very pose takes place. It's like you read my mind! You have a great talent and I dearly hope you hone it and use it to make more amazing artwork. Keep up the fantastic work!
This is a very beautiful piece of work, especially in the context of the Mass Effect story. This picture really implies something incredibly sad (the Quarian extinction), and illustrates it much more emotionally than the game did (I kind of wish a scene like this was actually in the game) but enough about hypothetical(s).
What was Awesome: your choice of colors, I like the drab look, I guess I might have been tempting to go for high saturation colors similar to the game, but I'm glad you didn't. Taking the colors roughly shared by the two characters i.e. purple and dark purple, and exemplifying them really goes a long way in giving this picture character.