I like the mix of the old CT LBB and the images. Small suggestion though: I found the world on the Terran one to be a bit too big. Alternate cover art for this one that still manages round is the symbol from the Solomani aliens book for the Terran Federation (The one that has a vaguely UN flag look to it....).
I like the new Mercenary Cruiser one... that's good, though I'd have been tempted to save that art for your Book 4, 5, and 6 release (for advanced chargen). I associated Mercenary Cruiser with Book 4 :0).
For Machines, there could be other choices - A Tigress (very High Gaurd!) would make an excellent image and still manage round.
For the first book, I like the Sun X-ray, but it would be nice to have a small lab ship or scout ship somewhere on there to give the feel of 'hey, here is a foreign star and look, somebody is travelling there...'.
For the contacts book, maybe hunt around the web for a good cat's eye.... that might make for a good image and it could be envisioned as an Aslan eye....
I will disagree with the other poster who suggested 'action pictures'. Not because you can't do good ones, but because they come off often looking a bit cartoony (MT Player's Manual cover which was so reminiscent of Paranoia game art) or just subtly wrong (T20 cover... the Vargr just didn't match my old CT image of Vargr and I hate seeing lasers in a hard sci-fi game!). I'm happy with a simple theme like the round thing.
The one for Rebellion, I'm just not sure how that quite captures the idea of rebellion... Actually, what might capture the idea of tearing apart would be some sort of 'fireworks-y' kind of image - you know when you watch a firework go off and little lighted bits scatter out in a vaguely spherical form? Something exploding would be what I'd be shooting for here (imploding also works, given the Rebellion). Another choice would be something like a Terran world, which would be basically blue/green to start with, but with apparent large scale fires, blackened areas, etc. - reflects how a normally lovely world is torn apart by the Rebellion...
Just some thoughts. Bon chance with le version francais! (Mon Franglais est tres horrible, c'est frommage!)
:0)