Quoted from luvthatapex2:
I think the best toppers follow the theme but show something different than the backglass. Since she is on the backglass, an alternate topper would do just fine without her on it.
I agree it's way more interesting to make the topper compliment the games theme vs just duplicating stuff already there. The Stern topper for TMNT prominently displays the TMNT logo just a few inches above the exact same logo on the backglass.
For the DIY types I saw this spooky old timey movie projector Halloween decoration at Lowes the other day. When triggered, the two reels spin and it projects a flickering pic of Frankenstein on a nearby surface. You could replace the internal slide from Frankenstein to one of Elvira or the movie macabre logo and trigger it to run whenever you are in a haunt. Totally fits the theme of the game and is $970.01 less than the Stern topper.