If we talk about a new online user than a link should be in text form
as "click here to enlarge" or any similar textual indication.
For a regular online user : We can use more interactive icons /
buttons or symbols to indicate them that he needs to click here for
the related action.....
But still some kind of textual indication should be there because
some users may use text based browser or may not even see images on
normal browsers also due to slow internet speed. So according to
standards the links should be represented in a textual form to make
it accessible for every type of user.