You can already see that you crafted a specific item when you look at it on the marketboard. For example, if someone buys a piece of armor that you made, and you happen to examine that person, you will see your armor with your character's name as the one who crafted it.

I always thought it would be a nice touch if we could "stamp" our items with a seal, kind of like how Ironworks does, something akin to free company crests that players could enable or disable if they wanted to.