The whole focus in version 1.3 was to make Image Sitemap Pro a Multisite compatible plugin. Few users have requested this feature. More so many people use Multisite feature of WordPress if they have more than one domain.With 1.2 live and stable it was time to make plugin Multisite.
The plugin was made compatible with Multisite functionality of WordPress and version 1.3 was rolled out.No other enhancements were taken up in this release. The sole focus was to add this functionality. Also there should not be any adverse impact on non Multisite users.
A minor release is planned after 1.3 to address bugs and code improvement which may have been there after major change in 1.3 despite best efforts.