After migrating a Sharepoint 2010 Site Collection to Sharepoint 2013 and then upgrading the look and feel to SHarepoint 2013 look and feel, the sites run successfully with the following lost functionality.
When attempting to select a different Theme (Change the Look) only the current theme is available to alter colors and fonts. No other themes are rendered to pick from.
If I create a new template from a site created fresh in Sharepoint 2013 and then create another site from that template then the full set of themes is available. I imported both templates (the one from a migrated site) and the one from the non-migrated site into Visual Studio 2012 and could find no difference (nothing seems to be missing from the migrated template in terms of structure). But any site created from the migrated template will be created with no themes available in Change the Look.
Earllibby