You need to enter the address of the image itself onto your Avatar URL (on your profile), not the address of the page that it is on. To find the address of the image, right click on the image on the website it is on, click properties, then copy the address that it says.
The things you mentioned with the symbols and flags that most people have as the avatar are our Euroharmony badges. They are created using a program that was on the Euroharmony site before the crash. They represent the awards that pilots had and the rank that pilots had.