A pic of my car
 

How can I add a pic of my car beside my name am I allowed too?

Embed a picture link within your signature instead, as you see many people here have done.

and shrink it a bit.

What you're asking for is an avatar.

When a user has at least 100 posts, he or she can send a PM to the owners of the site and get one set up.

I like what the other posters of this thread have done and did that myself after having an avatar for a long time. This way I can change it out any time I like.