How do I enlarge my Avatar on my profile?

[walker starr]

I want my truck to be bigger. What is the largest size picture that I can select as an Avatar.  Seems like no matter what size I try, it stays the same size when I post.  However, I see other people's Avatars show up larger.  

[Charles Sloan]

You need to crop it so its square, the board reduces size.

[walker starr]

   It was never a square truck.  It when new was rectangular in dimension.
   True it is an old truck.  It did see a lot of service.  I feel its the perfect
   avatar for someone like me. I would like it to be larger but I feel cropping
   it would diminish its meaningfullness.  Isn't there some way with modern
   technology to enlarge it without cutting it?  Thanks for any consideration.