Jennifer Aniston on the DVD cover
It's no surprise that when the film first came out it was just the leprechaun on the poster with the tagline "Your luck just ran out" and then once Jen became famous via Friends they tweaked the tagline, added her name and then her picture on the cover to help promote the film and sell more copies.
What I thought was interesting though (another marketing ploy of course) is that on the new cover the pic of Jen is more recent and how she looks now and definitely not what she looked like in the film back in 1993 lol
Here's the three posters:
Original: http://www.moviegoods.com/Assets/product_images/1020/209996.1020.A.jpg
Name added: http://1.media.collegehumor.cvcdn.com/a/9/collegehumor.b668f0bae047408 c73ee814962d17c33.jpg
Picture added: http://blogs.amctv.com/movie-blog/leprechaun%20poster.jpg