When images in a theme are saved, they are saved with the contextPath. If the contextPath is changed, the images will no longer show up as they still have the old one.
To fix this, re-save any theme that is not rendering properly. This will trigger the theme to save the new contextPath instead.
A little more information can be found here: Change of ContextPath
Powered by Atlassian Confluence 6.1.0, themed by RefinedTheme 5.1.17