With an Atlantic Common Brown Octopus, what type of octopus should i expect to see when i pick it up at the LFS? Like what kind of octopus come from the atlantic ocean and is thier any pictures of them?

You could expect anything from a vulgaris to a dwarf mercatoris. Some common atlantic octopuses sold as pets are : Vulgaris, Mercatoris, Briareus, Hummellincki (also called Filosus). Im sure there are more, thats just what i can think of for now.

Atlantic Common Brown Octopus is the label the LFS uses when it doesn't know the ID...

It's like getting a "common" crayon.

At least you know it's from the Atlantic.