Binding to visual objects in the model?

Imagine an application with a large amount of graphical interactivity, where users can use tools to modify the way a product looks, or how the packaging is designed, etc. Perhaps even think in terms of a WPF MVVM "Paint".

In WPF the obvious way (I think at least) to allow users to manipulate the designs is using a Canvas control. When they have finished designing the "look" it needs to be saved to that users data so that they can "use" their design later on, or come back and modify it again later. This Canvas can be saved to an entity then as either a binary object, or perhaps better still, as a string containing the "raw" xaml, which can then be parsed in/out.

To add a bit more complexity, some of the things that the user may have positioned / resized / etc. are linked to data properties, let's go back to my old DVD example; say the user is designing the cover art for a DVD they have just uploaded, they want to be able to select from a range of "template" DVD covers which are essentially just Canvases that contain text fields that are linked to underlying properties of the DVD. eg. a text field called "Title" doesn't get printed with the word "Title" it is replaced with the DVDs title property.

I'm struggling as to how best to achieve this sort of behaviour, in terms of how the data bindings should work, what objects should potentially be there-own Views / ViewModels, etc. Also, I'm not sure if saving them in the way I described is in-fact the best way to store it all...

I've taken a look at this: http://stackoverflow.com/questions/975602/mvvm-pattern-for-a-paint-like-wpf-application 

But I'm still struggling to see how I can put this all together... Any help / tips / pointers / opinions mucho appreciated!

I like the fact it doesn't involve storing *.xaml in the database and then using that in effect (once it's parsed) as a view, which seems very wrong in an MVVM app.

However, I have some questions regarding the notification of a property that's been updated in the Entity... Say I have an entity called "IsBold" and it's a boolean; if I have a function called "MakeBold()" in the entity that sets the property to true, how does the Binding get notified that it has changed?

And the code snippets:

Some Xaml:

It doesn't. It just knows about the ValueConverter the same way it knows about the ViewModel. The details are hidden in the ValueConverter. Converting directly in the ViewModel is another option if you have a ViewModel in between. I personally don't like using visual types in the ViewModels, because that means my ViewModel needs to know what control I'm actually using in the View. It shouldn't have to know that. The ValueConverter keeps these details independent.