I liked how the default browser bookmarks just had an image of the website logo, for a clean and elegant look. I thought it would be neat if I could make all of my bookmarks look like that, instead of the ugly screenshot of the page. I started looking around, and found that they are located here:
/var/luna/data/browser/icons
They are named
thumbnail-xxx.png. I simply opened each of the images in photoshop, and edited them to fit my needs. Make sure when you save them they are named the same thing.
There are also files for the smaller icons, but I only felt like dealing with the main thumbnail for now. Just thought I would share in case anyone else wants to know how to do this.