I wrote this user control which may help, it will display messages with a progress bar spinning to show it is currently loading something.
<ctr:LoadingPanel x:Name="loadingPanel"
IsLoading="{Binding PanelLoading}"
Message="{Binding PanelMainMessage}"
SubMessage="{Binding PanelSubMessage}"
ClosePanelCommand="{Binding PanelCloseCommand}" />
It has a couple of basic properties that you can bind to.