Our poster is just learning this game and I think he is making a good start.
Agreed, however it has a very MS Paint look to it. I did my degree in something totally different to design like this, however i've had to make up a few corporate posters and things for events at work.
OP
As Disco said, think about the background, it's not land rover related at all. Linked to the background, think about how the images in the foreground react to the background. You've got the words DEFENDER seemingly randomly placed on the right with a black background to the image. That's not ideal at all, the black background makes it look fresh off of cooltext.com. You want a transparent background .png file, alternatively, google the defender font, download it and make your own. The company logos in the bottom right aren't aligned and also are not uniform in size. If you're using something like MS Publisher, there's an auto snap/guide for aligning images to images around them. Use it. It'll make it look neater, maybe also put them next to eachoter without a space between, at the moment they look a little haphazardly dropped.
The text in the bottom left isn't a great font, it's not a good colour either and there's a little too much text.
Look at apple posters, less is more and they're clean with a minimalist look.
this one is a little old but still:
RE: the text on the bottom left:
Try to cut it down, we don't need to know everything, that would be mentioned when they look up the website! You need fewer but larger words, statements that are quick to the eye.
just my 2 pence.