In that link down there is a screen shot of two pages in my default site pages doc library. I am hoping someone can tell if that difference in icons means anything special.
I believe the first is the icon for Web Part Pages, while the other is used for most other web pages. From 15\template\xml\docicon.xml:
<Mapping OpenControl="SharePoint.OpenDocuments" EditText="Microsoft SharePoint Designer" Value="icsmrtpg.gif" Key="SharePoint.WebPartPage.Document"/>
The image files are in 15\template\images. You can confirm them there. The other image (ichtm.gif) is used for several file types including asp, aspx (that are not web part pages), and htm/html.