Great job! I like the overall color scheme you chose, so that despite the colorful characetrs, the portrait isn't too bright and cheery looking. I also like that you chose the cast from the animated series Justice League.
That is really impressive. Despite the brushstrokes this looks incredibly realistic! Although all the characters seem to have a very similar look on their faces, they look serious and determined. I especially love the shading on the green part of Green Lantern's costume.