Cards are allowed - because, well, they're cards. Howeverm other items, that are not cards, are not allowed if they are not made by a card company or distributred with cards.
So Boeing cards - allowed. Boeing stickers - not allowed.
https://www.tcdb.com/FAQ.cfm?ITEM=OtherCollectibles
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).