There could have been more contrast in this image. The strongest points right now are all the bright colored areas; the shirt, sleeves, soles and the obnoxiously yellow wall. Oh, and his hair. The other colors are really flat. The blue jeans and red jacket are probably the same value. Blegh! Very boring.
Things could easily become more interesting just by adjusting the contrast and saturation. I mean, just look at the space background. Very cosmic! Even the Custodian (who has obviously undergone some extreme aging) seems to pop against the darkness around his head.
Now if we take a look at a grayscale of the image, below, we see how boring things really are even when the saturation was given a little bump. There is just to much gray in or near the same values. This picture needs a major overhaul. Balance comes to mind. Perfect balance.