What can I say !
Before, this image name was "Happy boy".
After I posted a thread about image name..., and having some suggestions from our DT's Admin Petarneychev, then I changed it to "Smiling asian boy".
Today, I got one sale for this image with keyword search "asian boy smiling". It exactly match with image name just in different order and this image appeared on the first one of the first page(sort by relevancy descending).
Here is the image....my baby boy:
Thanks the buyer and Petarneychev! :)