How to get images/resources if the Vaadin app is only UI

Hi,

I am trying to work with OSGi based Vaadin app.
The structure of my app is that there is a Main module which is my web app and then there are sub modules which are just inheriting from Vaadin UI i.e. they are no web application.
My question is, how can I add resources/images to my sub module which are just plain simple UI.