Hi,

There are two ways to do this effect.

1) Upload two images, one color and one grayscale, and change them on hover with css. This method however could not be achieved without modding the core files of Shoppica Banners module.

2) Use some javascript plugin; you will only have to modify the frontend in this case. Here are some solution to do what you want:

http://www.pixastic.com/lib/docs/actions/desaturate/

http://webdesignerwall.com/tutorials/html5-grayscale-image-hover

http://www.permadi.com/tutorial/jsCanvasGrayscale/index.html

http://www.pryde-design.co.uk/2011/08/greyscale-jquery-plugin/

Hope this will help you.

Best,
ThemeBurn team