No. On the contrary, some of the most powerful mystery, thriller, and horror films ever created have taken the implied route with a great deal of success. One of my favorite examples is the Alfred Hitchcock Vertigo. As a master of suspense, mystery, and horror, Hitchcock created an atmosphere rich in fear and dread without showing any real violence on screen. Another historic example is the film What Ever Happened to Baby Jane this is truly a horror film, as the antagonist, the former child star Baby Jane Hudson, slowly grows more and more insane and desperate to relive her glory days of yore. Despite the fact that Ms. Hudson commits horrible atrocities, they are shown with surprisingly little blood and gore, and the depictions are conservative on screen. In my opinion, this actually works to increase the tension, as opposed to all-out gore like modern killer films.

I would also like to draw your attention to the fact that both the book and the film aren't really about the murder as much as they are about a family coping with a terrible tragedy. In this aspect, it doesn't matter how much of the murder is shown. The real mystery lies in the mysteries and philosophies of human nature, just as it should.

I have seen the movie and say it was enough what it was shown.
The story is about a little girl being killed, not a thing that you want to see. I think the director presented well. They showed when the girl was lured by the killer into a room with dolls and the first moments when he stopped her to leave. She started to run through a field. Then the actual scene when she is killed was not shown, which is very good.
Movies don't need to be graphical; there are other ways to suggest what happened and induce emotions into the viewer.
Stanley Tucci was uncomfortable about his role-he wanted to film that scene as fast as possible but it took 2 days. Tucci thinks there is an inflation of movies about serial killers out there. Even at Oscars night, when he was nominated, he seemed displeased with the clip that they presented.
As I wrote in the Mahalo page http://www.mahalo.com/stanley-tucci-acceptance-speech ,
"The actor was reluctant first to accept the role because of its sensitive subject, but as he declared ""The Lovely Bones" is a beautiful story about the exploration of the loss"
read more at
http://www.canada.com/entertainment/movie-guide/Tucci+lovely+role/2463731/story.html

I loved the book and waited eagerly for this movie to come out. I was slightly dissapointed that they took out a few of the character developing scenes but when it came to the scenes of violence I was relieved they only hinted at what happened instead of keeping the graphic death scene from the book. The first time I saw this film I braced myself when the killer lures Suzie Salmon into what he says is a clubhouse built for the neighborhood kids. I was relieved when the scene ended without showing her rape and dismemberment. The violence was implied enough with the way he went after her when she tried to escape and the blood shown later on.
The scene in the book was traumatic and long. I felt like I suffered along Susie and it added to the beauty of the book overall. Imagining this scene as you read it is very different from actually having to see it portrayed on screen. I think it would have been far too shocking for most audiences and would have taken away from the beauty of the film. Many viewers might have even walked out of the theater. The point of both the book and the film wasn't to shock or scare the audience but to show the beauty and new beginings that can grow from loss.
In the end I think Jackson did an amazing job portraying what Susie suffered without actually showing it. In interviews with Stanley Tucci he said that he had a hard time with the scene in the clubhouse and would appologize to Saoirse Ronan, who plays Susie, and ask if she was ok reapetedly. The actor obviously agrees with Jackson that the scenes of violence were violent and creepy enough. When we see Stanley Tuccis character soaking in a bathtub a couple of scenes later, the floor scattered with his blood-and-mud-soaked clothes I think more than enough is implied. We're still shocked, we still suffer along with Susie, we still feel for her. But we don't have to loose the beauty of the film and of Susies own perfect afterlife under the images of violence.

Note: I did have a hard time watching this movie the first time because Stanley Tuccis character reminded me of this guy.

in my opinion no, you really don't need all the greusome and graphic to have a good thriller told.