Here are 6 post cards from a set.
The set though, had 100 cards in it! So many! And...they're kinda wierd, so let's get into it.
So this set of postcards was clearly done around the time of Sonic 3 or so, after Sonic CD came out. 1996-97But, instead of using normal art, whatever company this was, decided to do CG scenes to make all of the items. But, due to the era, CG was still really hard to do, and, even harder to get it to look right and actually work.
However, they didn't let this stop them, so the result is dinner-plate-eye dino Rexxon here along with kinda-dumpy Metal Sonic. The models have lots of problems, like Tails with huge eyes, not knowing what to do with Sonic's eye border, stumpy Metal with poorly planned eye & the usual really flat/blah texture for the background. Notice also that they've got AOSTH Robotnick in there instead of Eggman and he looks even stranger.
The problems arise further when actual scenes from the games look better than the cards do. Remember: in this time there weren't really cinematics & etc, CD had animated/hand drawn parts because the CG just wasn't there and they didn't want it to look bad. So it was common that merchandise would use something OTHER than the game/shots because you could 'do better' than 8-bit Mario screen cap with some cute Mario art, for instance.

But then you've got dumpy Metal in some like...super pixel clouds & a prickly dot and it proooobably wouldn't have impressed anyone at the time.

At the right are more of these cards!
And this set brings more attempts that sssooorta work. You've got the Sonic vs Metal race but the background is vague and wierd. They did attend to Tails tails in 'twirl' shape there for the 2nd one, but every head for him except where he's in the half-pipe has the bangs wrong. They add Knuckles, but (as is common with UK art for whatever reason) they're obsessed with making his eyes really tall, which always looks bad. Also look at the thick sole to the shoe/frankenstein style. Where is 3 blue squares area supposed to be with Tails?
The combination of awkward backgrouns and kinda blobby CG that's not fabulous (or particularly shaded?) really screams "Era! Late 90s!" , so these are certainly reflective of the time.
The last 2 images shows the back (plain white, 1 small actual stock Sonic art in the corner there) and the front / cover of the set which shows 2 cards, tells you that there's 100 in there & then pastes on the CG for Sonic, Tails & Knuckles, then puts an orbinaut at the top. 

Scans by Caleb