Saint Theresa of Avila advised the nuns in her convent against praying or meditating upon Christ using a picture of Christ. She explained that for the thing to work, you needed to feel that Christ was actually present in the room with you. Meditating with a picture would be as absurd as sitting across the table from someone, yet conversing with their picture.
That's true, but I think a better way to go would be to acknowledge the living presence of Christ in the room, and then ask if he'd do you a favor and stand right behind this picture, because that would be very helpful.