Animation cannot change property values for a property path that does not exist. The "Image" you are trying to manipulate does not have "Rotate transform" you should add it and it should work:
<Image Width="20" Height="20" Name="SomePropertyIcon"
Source="{Binding Path=Value.SomeProperty, Converter={StaticResource somePropertyToImageConverter}}">
<Image.RenderTransform >
<RotateTransform />
</Image.RenderTransform>
</Image>