Mosaic Image Generator

Hello,
My girlfriend has a cooking blog. She wants to have a mosaic of images of different recepies she posted on her front page. When a photo is clicked the viewer will be redirected to the following publication. I want only the main picture of the recepies to be used. Not any pictures of the cooking project. Any ideas how can I do that? The inbuild option of the wordpress gallery can generate mosaics, but when they are clicked only thing is that a bigger version of the image opens.