CVS Import images

That should work indeed. Do you get the image entry for the product in the back end (even if the image is not displayed) ?
Did you change the upload folder in the config under the tab files ?

So you have the image entry but the system cannot find the image when trying to display it, so it displays the default image instead.
Could you edit the file administrator/components/com_hikashop/helpers/images.php and add the code :
echo $path;

just after the line:
function _checkImage($path){

and try again to look at your product edition screen on the back end. That will display the path where hikashop search for your image. Your image should not be there...

So that means that the file /home/tntwebho/public_html/dev1/paintings2/media/com_hikashop/upload/HS2399.jpg does not exists. Please double check it.