how do i get a photo of my car to come up when i reply posts?

http://www.slantsix.org/forum/viewtopic.php?t=4434

You can use the img html lines (from the example in the previous post)
either in the body of the reply message (for a one time deal) or put it
in your profile's signature area (to get it everytime).

The key is to have an image of your car posted on the internet.
For a signature image that comes up automatically, please keep that image small so it loads fast and does not run the message text off the screen. (200 pixels across is about all you need, over 400 pixel is a problem.)
DD