I figured this was worth posting, since I've gotten some PMs/IMs about it over the last few months (and hell, I wanted to know some of this stuff myself! :ugh:)
-The thumbnail picture size is 150x103 (you could actually check this by looking at the properties of an existing car's thumbnail picture)
-We had some glitches with screenshots being certain resolutions or file types in the past, but as far as I recall they have been corrected -- though I still suggest to use 640x480 JPEG (with some compression).
-FYI, if you use JPEG, be sure that your car is not red -- red is notorious for having the worst picture quality with JPEG.
-On the subject of car colors, try not to use dark colors -- people in most cases won't want to waste the time downloading your car to see what it looks like in the game if they can't see it in the screenshot. I personally use whites and silvers or other similar bright(er) colors.
-If uploading for NFS High Stakes and your car has engine sounds, you can reduce the file size by deleting the SCARENG.BNK file from your CAR.VIV. I want to say it was Zpectre that mentioned this in the car engine editing guide that that file does nothing but take up space and serves no particular purpose.
don't let the "mecha done with NFS" topic fool you ... I still intend to remain a part of this staff so long as it is RealLife(tm) feasible. don't hesitate to PM or IM me if you have questions -- it's what I'm on staff here for!
thanks,
THE MANAGEMENT