It looks like you did it right, but that the link is one of those sites that doesn't allow outside links. The picture shows up as a small white box with a red X. If I load the address into my browser, the picture shows up fine, and also shows up on the MercedesShop post. So it isn't you, it is their linking policy.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E