greger,
the spacers in your picture are "lug centric" which essentially means that the lug studs both align the spacer and the wheel and also carry the weight.
Here's a link to a page with a pic of a couple of different types of "hub centric" spacers:
http://www.maximummotorsports.com/i.../store/index.php?main_page=index&cPath=48_134
the back side of the hub centric spacers are machined to ride on the hub of the axle or hub just as your wheel would be. The front side has a lip (just like your hub) for the wheel to be centered on and to carry the load via the hub and not the lug studs.
I've used them on my Mustangs to fill the gap between tire & wheelwell, and my personal preference is the hub centric spacer. I've used both the type where I installed longer lug studs and slipped the spacer between the rotor and the wheel and the type that bolt to the hub and extend new studs for the wheel to bolt to. With the type that you bolt to the hub and then bolt your wheel to the new studs, remember that unlike most aftermarket wheels, many factory wheels are machined flat on the back of the mounting surface (instead of having recesses or dimples like most aftermarket); something that would necessitate your having to trim any factory studs that would protrude past the mounting surface of the spacer.
Whether hub centric or lug centric, spacers machined out of a single piece of billet are higher quality than spacers that are stamped out. Whatever type of spacer you go with, whether hub or lug centric, do two things: (1) torque the spacer and/or wheel to specs on installation and then go back about 100 miles later and retorque them. You wouldn't want to be riding down the road and have your wheel pass you by.
One more note: if you plan on using 1/4" spacers, you probably will not need longer studs. However, you need to make sure that you have enough stud protruding through past the spacer to catch enough threads of the lug nut. I know that one manufacturer recommends getting at least eight full turns on a lug nut and another recommends catching at least as many threads as the measured diameter of the lug nut (example, if the lug nut is 1/2" diameter, there should be at least 1/2" of threads protruding past the wheel for lug nut installation.