Have you tried all locations? under navbar.. etc..
there could have been a template change in forum home for 3.81
As I dont use that feature i really dont know.
If you use custom location your HAVE to edit template.
It only works if you actually have validated images..
(You said: fresh install)
Sometimes on fresh install.. images are not validated automatically
setting in userpermissions validate this users images.. means that you have to validate them by hand.
As admin you still can see them.. but they are not validated.. so they wont show on forum home.
(if you change this setting you still have to validate allready uploaded images. Only new images after you changed the setting will be validated automatically)
Thats my 2 cents