BTW-1, Regardless of where you mount it, the sticker would benefit from a white background to make it pop. A lot of what you see as white on your computer screen will take on the color of whatever it is applied to, so, in the case of a windshield it will have a lot of clear in it (the clown head is only mildly translucent).
Here's the windshield sticker, backlit with an LED shoplight.
Comparing them, the body sticker (against a white car) looks far better, but I'm waiting for the facial expressions of the PCA crowd when they look close. I'll be swapping the windshield version for the more PCA-looking version (Mitch's) but may leave the white adhesive cover on the back to make it stand out more stuck on the windshield. I might also play with adding a white master as the first layer of the image (if I can) so it won't matter what color car you apply it to.
I am having so much fun with this........
BTW-2: The Silhouette sheets come 8 to a pack for about $8 bucks at any place selling Cricut supplies and I can print 3" dia. stickers six at a whack.
Mitch/Carlos: Can you add a white base layer to your last images? That should do it.