What I missed in the store (apart from I-Deal payments, a Dutch online purchasing system) was a nice Twister Shirt.
So here is it in word: Simply a front view of the car, from a low angle, in such away that the car looms over whom ever looks at it.
All this not to detailed, but still recognisable as the Twister, using the colours Yellow, White, Black and a few shades of grey(not all 50) possibly even read for indicators and the occasional blood spat.
Underneath you could place a witty text if you must, such as: "Screw You" "Hang on to your helmet" "Look out! it's A Twister" or something that is actually funny.
I don't really see any need for a print on the back, cause I only admire my front in the mirror.
Here something I drew in Paint, to prove that text is sometimes more useful than poorly drawn concepts.
hmmm... your idea reminds me a lot of my idea