I remember back in the 70's you'd see that Good Sam sticker on RV's of the day and since I was just a kid, I didn't really know what it meant.
I thought they just bought their rigs from the same place!
Anyway, the places I go don't do the discounts and such for membership, so I've never been one.
To the OP, it does seem to be that the actual link you have for your logo pick is no longer active, so that's why it does not show.
If you right click on the logo symbol and select 'copy image address' and then 'paste' that into your web browser, you'll see the link does not exist any longer.
I think you have to find the logo image again, and update your signature with that new address!
***Link Removed***