bkg_credits - 
GOOD / ALMOST PERFECT.
bkg_entry - 
As
Lynce said, this could be better.
bkg_garage -
GOOD / ALMOST PERFECT. I think the "circle" should be more rounded and the shadows could be better. Right now, if you spin the car, it looks like it's floating.
bkg_lesson -
GOOD.
bkg_multi - 
GOOD. The only suggestion I have is to make more backgrounds, using different cars.
bkg_options - 
GOOD. Maybe it would look better with less tools...
bkg_replay - 
PERFECT.
bkg_setup -
PERFECT.
bkg_track -
PERFECT.
bkg_training - 
Not as good as the rest. The cones could be represented better.
I like this pack very much. I only said "bad" things about it, because I want this to be perfect.
P.S. I use 1920x1080 resolution.