I installed your plugin on a test bed site and would like to share a few thoughts. This is not a trouble ticket, but feature suggestion.
I have read a few forum threads related to the styling of fancybox, they all indicate that in order to change any behavior or styling of FB one needs to edit the code or the CSS. Not that I would shy away from doing that, this is not a viable long term solution for your plugin. First, any plugin update will eliminate the changes. Second, while all other <name>Box presenters offer configuration settings that are tied to a UI doing this in the code is simply clumsy.
Do you plan to provide a settings UI for this plugin, free or premium versions? Why not use a regular installation of FB and hook on to that?