I think the image is a little flat in two regards, 1) the processing leaves it a bit flat, there are a number of ways to beat this one on the head which could make it a stonger image 2) the composition makes it seem flat, the position of the monkey within the frame is uninteresting, good from a scientific point of view but a bit boring from a photography point of view. I think jazzing up the composition could have gone a long way to improving the depth of the image, even as simple as a off centre composition may well work here.
With that said, working with teh image you have, if it does not have enough impact, do as the film makers say, 'go wider or go tighter' in this case I reckon go tighter and work on teh processing. Also i think adusting the vertical tilt a fraction may help in giving more of a symmetrical frame.
here is a 30 sec crack on the low res version which may give you some alternative ideas. if you want it removed or object to your images being edited le me know and i will remove it.
He/she has some intense eyes, possibly working that avenue will help.