Being the idiot perfectionist that I am, I actually took this one off (I didn't cut the top edge properly).
I'm just printing these off of my regular old inkjet. They don't look too bad on top of grey or relatively light colored spots. But trying to put these stickers on the black parts hasn't been working out too well.
It's definitely been a learning experience trying to get these right. First, I tried to print out some light-grey stickers, but it was ridiculously hard to see 'em on the Blackjack.
Then, I tried a sneaky method to white-back some of the lighter stickers (using those little white-out/correction tape mechanical rolling thingies). But trying to remove the excess white background was messy and didn't leave stickers looking all that nice.
Just a few hours ago, I tried an even sneakier method. This one involved using the correction tape method above and printing the light-colored stickers with a black background. I'm letting them dry right now.
If it works out, I'll post some pics.