People who wanted SharePoint 2010 Look & Feel inside SharePoint 2013 can still have it. This article provides the procedure to do that.
Step 1: Open Central Administration
Open you SharePoint 2013 Central Administration screen.
Step 2: Create new Site Collection
Choose the "Create site collections" link from the Application Management group.
Enter the information like Title, Template, Administrator and so on.
Step 3: Choose SP 2010
This is the most specific step. Choose 2010 for "Select experience version".
Enter the other parameters & click "Ok" to create the site collection.
Step 4: Test new site
Now you are ready to test the new site collection. On entering the new URL, you can see the site below.
Now you are ready with the SharePoint 2010 look & feel for a SharePoint 2013 site.
Please note that SP 2010 is not just a theme but an experience. Some of the advanced features of the SP 2010 experience will be missing.
References
http://msdn.microsoft.com/en-us/library/jj927174.aspx
Summary
In this article we have explored how to create a site collection with SharePoint 2010 look & feel or experience.