I installed the Win8 app called "Logo Quiz" the other day and noticed that the authors used a default splash screen image that simply contained an hourglass:
I found this definitely curious because a splash screen, while serving the same purpose of the hourglass–namely giving the user something to look at while an app is loading–is also an app's first opportunity for promoting their brand and creating a sense of identity in the mind of the user. So having an app's splash screen contain nothing but an hourglass works, for sure, but can be made so much better. I certainly hope that Logo Quiz improves upon this in their next version, because they do have a much more interesting tile image to serve as a basis.
At the same time, it's clear that some of the blame for this misunderstanding lies with Microsoft's early app templates in Visual Studio, where the default splash screen image from those templates showed a clock face:
This could easily have been interpreted to say that the purpose of the splash screen image is to show an hourglass representation of some sort, but indeed, that's not the point at all. This is one reason why the current templates now just have a box with a big X through it as if to say "please don't use this image!" (though some apps still do!).
In the end, always remember that the splash screen image is the first thing a user sees when they tap your app tile, so you want to make it as engaging and inspiring as you can–make the user happy that they tapped your tile! Help them to look forward to spending time in your app! As one example, I offer the splash screen of Pinball Fx2, an app with which I spent far too much time over the Christmas holidays:
I would almost venture to say that a great splash screen image is one that makes your users wish the app would load faster–and then, of course, you're in great shape to use an extended splash screen….