If you're still working it - then I'd say it's going in the right direction (my tastes). I see you make
signs clearly now....Which is the goal. Play with it. You're getting on the right track.
My question to you would be....If you looked at JUST the thumbnail - is there anything you feel could use some improvement? Also...Is the rear window square? I doubt it. - Take advantage of your WHOLE canvas. If you can't read the detail portion - I'd say maybe make it larger. Can't read the number? If you have room - go bigger.
When I design - I do all my sketches first - eliminate the bad ones (which is usually about 20 or better). Work with the one or two I like - then see what elements I like from each and try and blend them.
Is there anything in your design that YOU don't like? If so....Make whatever it is that you don't care for go away. Repeat.
In the end....You may be on to something.
Also - do yourself a favor and take the advise that has been given here thousands upon thousands of times. Design in Black and White.
Also - keep in mind that your "black" is actually VERY glossy, semi transparent and highly prone to glare - All of which are design challenges. (I.E - Keep it simple and bold.....IMO)
-Chad