Hey there,

Attached 10 pics to my account and created a thread for Earthbound with board and box pics but when I click an image or click +6 others, I get

Forbidden

You don't have permission to access /_usermedia/attachments/ on this server.

Are you putting the pictures in the thread itself or just adding them as an attachment?
Have you tried using the vintage.nintendoage site?

EDIT to ADD: I see your FS thread, looks like you are trying to add them as an attachment. Pictures are probobly to large. I click on the only one that did post and after waiting 30 seconds for it to load, the picture was twice the size of my screen.
Try making the pictures smaller and uploading to NA again.