I recently changed the loading indicator to make it look a little better than the standard one.
Attached is a sample project I did to work it out. It involves changing a few standard Vaadin styles.
I have extended the halo theme so if you look in there you will see that it currently implements a pulsing dot I got from this site http://tobiasahlin.com/spinkit/
This animated spinner is done with CSS and these are the styles used.
There is also commented out styles in the theme extension that replaced the normal animated GIF that Vaadin uses with a gif I generated on https://loading.io/ These are the styles used to change the animated GIF to the one I created.
LoadingIndicatorPOC.zip (231.0 KB)
Hope that helps someone.