Nope, you don't need to know what they look like at all. Though, for reference, I've looked up all the ECs and have two pictures of each. Google image search is helpful for most of them, but there are a few rare ones that have few pictures on the internet.
If you desire a better connection with a particular crystal, it would be a good idea to know what it looks like. Though, like I've said, it's not necessary.
Good question. Remember, the only silly questions are the ones you don't ask.

Sage