spinner.gif not loaded from Valo theme?

In my project implementing Vaadin 7.7.6 currently, the page loading indicator spinner.gif cannot be loaded at application startup.

Google Chrome's Inspector (Ctrl + Shift + I) says:
Failed to load resource: the server responded with a status of 404 (Not Found)
Mouse over on missing resource spinner.gif shows me path
http://localhost:8080/my_project/VAADIN/themes/my_theme/img/spinner.gif

In Jouni Koivuviita tells:
"there's a suitable spinner GIF in Valo in valo/shared/img/spinner.gif"
which I found in

vaadin-themes-7.7.6.jar

I copied this .gif to my_theme's image folder and now correctly see a loading indicator on application startup.

my_theme's scss is based on the initial theme Valo from this Vaadin archetype:
<!-- https://mvnrepository.com/artifact/com.vaadin/vaadin-archetype-application-example -->

<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin-archetype-application-example</artifactId>
    <version>7.6.1</version>
</dependency

I wonder if it is intended that I have to copy the spinner into my_project's image folder first, or what the reason may be?
 

I finally got to the following conclusion:
obviously my_theme.scss, which is a copy of Valo's

styles.scss

which I saved to new path

my_project/VAADIN/themes/my_theme/

and extended it for our needs, is searching for images in subfolder

/img

now, which explains the "missing" spinner.gif.
Such, this question may be closed.