Category:SubDomain of wordpress.com
Subdomains are added manually. You need to add the Subdomain Page Boilerplate to this page. It's as easy as 1-2-3.
Currently thumbnails work for some subdomains, but not all.
This is a list of available subpages of wordpress.com in AboutUs.
Pages in category "SubDomain of wordpress.com"
The following 11 pages are in this category, out of 11 total.