There are many ways to do this, however, using the itemCommand event is probably not the best approach since you have said that you want the user to click on the image and not a command button.
What I would probably do is use ImageButtons instead of Images and in the buttons CommandArgument I would place the ID of the current product. You could then create a method to handle the command event of the ImageButton and just do something like this inside the method to get the ID:
ImageButton img = (ImageButton)sender;
int iPK = Convert.ToInt32(img.CommandArgument);
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