A simple link below each image with "View larger image", "Enlarge Image" or "[Enlarge]" should suffice. clicking either the text link or the actual image should take the user to the enlarged image
"Click here" is redundant if the word is an obvious link; web surfers already know to click on links. If the link is not an obvious one, it ought to be made more obvious. "click here" doesn't stand out as much as the change in text styles used to denote a link (usually underline but occasionalyl a simple color change or bolding, or both like on BL)