Ahh, rego sticker is the equivalent of our old "tax disc", which we haven't had to display for the last 8 years or so, its all on line. This is mine on my old car.
Here's a garden variety US registration sticker, this one from Florida. The actual vehicle plate number is matching, and displayed on the top left side of the decal to prevent people from stealing them and putting them on their own expired vehicles' plates. Each state has different colors, sometimes more than one, like 1/2 white and 1/2 green, etc. States also vary which corner you place the sticker as well. Notice the current sticker is just placed over the previous one. Failure to do this can mean a traffic stop. This photo is magnified about 4 times actual sticker size on a laptop screen(approx 2 inch x 1 inch). Personally, I like the way things like this vary greatly in the states, although it can be a double-edged sword. I'm fervently against concentrating government vs. decentralizing and distributing power, even something as seemingly minor as vehicle regulation.