In SharePoint 2010, we are able to use any of the pre-built Themes or customize any of them using just the browser. If that was not enough , we are able to use either Microsoft Word, PowerPoint or Theme Builder to create new .thmx files that could then be uploaded to the Theme gallery by the site collection administrator and made available for site owners and designers to use on their sites. The whole theming engine has changed and been reworked in SharePoint 2013. Everything is based on HTML instead of any proprietary format. The image below shows the actual …
