I have Safari 6.0.5 , Mountain Lion on a 2012 MacBook Pro, purchased as a refurb from the Apple Store.
Our local Apple dealer transferred over all my files from my old MBP including my bookmarks.
I have the same issue as the original poster....however, I have no file called Webpageicons.db on my computer. I miss my little bookmarks webpage icons.
I was the original poster of this question.
Your original computer should have the Webpageicons.db file present. You just copy and paste it into the same location on the new computer.
Otherwise just open and load up each web page, and the bookmark icon will appear. YOu have may to close Safari, then reopen to view the icon. Some webpages dont have icons, but the majority of mine do have icons.
You will then see the Webpageicons.db update (date and time).