You are not doing anything wrong, that is how it works. Your avatar looks great, but that has nothing to do with the image that shows up next to the item for sale thread.
The only way I know to get rid of that '?' next to your item for sale thread is to
attach a picture to your original post. What you did was add a link to a picture which really resides on photobucket. I much prefer to share photos by linking them to a photo site rather than attach them, but they will not show up in the for sale thread title when we do it that way.
I hope that makes sense.... my lovely wife says I complicate things when I 'splain
