I think the gui would look better if the text and items would have little bit of transparency. Then add a racing related background image (either a colored one with black stripes or b&w one with desaturated colors and reduced color amounts). I think background images look a lot better than just grey background color. And the little bit of transparency makes the gui look a lot more modern.
Also I'd prefer if the text would stand out more. It is a bit too grey and lacks contrast. Also on the bottom bar where you choose different pages of setup I'd prefer if the current selection was more clearly highlighted.
Also it would be nice to have some kind of car specific info screen there as well. Something that lists if the car is rwd, awd or fwd, type of shifter and gearbox, suspension type etc.. plus some "story" text to tell something about the car. Where it did race, who drove it, some specific rule interpreations, some history bits, some driving tips and info about what specific version of the real car the sim car is modelled after (is it lemans version of silverstone version for example). Just a text field so modders can add as much info about their car as they want. And I'm not sure if it is worth it actually to have separate tab for brakes for example because there is not going to be much stuff there. Seeing that the last electronics tab is already partially out of the view reducing the options little to make them all fit the screen might be preferrable.
I did make an edited screen to show some of the stuff I suggested, have a look here. I just grabbed the first pic for background from google. I made two quick edits. I think the colored one looks really nice. The text in those my pics looks horrible because I just increased the contrast for the text which made it blocky.
link:
http://imgur.com/a/DGUzh
As for those car shots I hope the environmental map for the cars is getting improved. I think it is the weakest link of rf2 graphics. It is super difficult to get realistic looking reflections from the car surroundings and often times the env reflections just look like the car is covered in milk. This could make the cockpits especially look potentially really amazing.