Need the form to pull a graphic based on user submission

Hi All!

Does anyone know what coding to place in the function.php to make it grab an image when the user selects a rating? I have been looking through the source documents but I think I am too new to fully understand which one I should be focusing on. Any help would be appreciated. I have a review website. I have a graphic already but I want to give the user the opportunity to rate the product they are reviewing (5 STARS! or 2 STARS!) whichever the user chooses. I am considering using radio buttons. (unless there is something easier)

This would be helpful because I have two other forms that I need to pull a particular graphic based on the information provided by the user.

Well, I am using the forms for REVIEWS (primarily). Being a review, the reviewer (user filling in the form) needs the ability to "rate" the product. As in 2 out of 5 stars or 4 our of 5 stars, etc.
I need either
A) the ability for the user to click on the graphic embedded in the form--as in actually click the star rating
OR
B) the ability for the user to select an option in a radio button and the function coding that would allow for a user who selects #2 to grab the 2 out of 5 stars picture.

Obviously, my preference is whichever is easier. http://reviews.cnet.com/ This website has the star ratings everywhere on multiple pages. My site is using GF to allow folks to leave a review on a myriad of educational products. Obviously being a review site---the ratings are considered necessary. I was surprised the ability to grab a rating field was lot already part of GF but since I cannot just create a rating field--I must make do.

Suggestions?