From the sound of it you're moving against the basic principals of MVC, that being the separation of Model, View and Controller rather than your desire to split at 90 degrees to that by using modules.
I'm not entirely sure what benefit you would get from splitting it in to modules any way since I would expect you to have one GalleryController. Where you are likely to have the most 'entities' needing grouping is with the views, possibly one or more for each GalleryController action, but they are in their own folder which gives the sort of functionality you are looking for anyway.
Finally there are the models. Obviously I don't know your project so I don't know how it is laid out, but the Models do not usually exist for the use of one Controller (or module in your case). For example - I have Models for Users, Companies, Vehicles, etc, etc. These models are a shared representation of my data structure and have nothing to do with modules as a user may see it looking at a web page. I can't split them in to modules because the whole point is that they are shared by the entire application.
So...in reality it is the Views which can get a bit messy, but they are already split in to folders based on their Controller. Having said that you can move them around a bit if that suits your needs better. For the rest of it there is no need, either because you shouldn't if you want to use 'proper' MVC (i.e. modular Models) or there's no need (i.e. only one Controller). And if your controller gets too big just create a separate module for any functionality in that you want to split out. I reckon that's as modular as you should ever need to get.