Thanks for the ask (and for the lovely complements! *blush*), and don’t worry - that is not an idiotic question at all :)
There are two sets of writings you could be referring to: The Key of Solomon (sometimes referred to as The Greater Key), and The Lesser Key of Solomon (or, Lemegeton).
The Greater Key is broken down into two parts (or, “Books”), and includes the various Planetary Pentacles. For example, here are three - here we see (from left to right) the Fourth Pentacle of Mercury, the Second Pentacle of the Moon, and the First Pentacle of Mars:
The Lesser Key is broken down into five parts (or, “Books”):
- Ars Goetia
- Ars Theurgia Goetia
- Ars Paulina
- Ars Almadel
- Ars Notoria
The Ars Goetia is, arguably, the most famous - to the point where the entire Lesser Key is sometimes erroneously referred to as “The Goetia.” It is also this section which contains the names and seals of the 72 Demons. For example, here we see (from left to right) the seals of the Demons Leraie, Asmoday, Furcas, and Belial:
I point out this difference to make sure we’re on the same page :)
The seals (Planetary Pentacles) given in the Greater Key don’t have any connections to, or with, specific demons. There are a few which have broad power over demons in general, but mostly in the same kind of way as the cinematic showing-a-cross-to-a-vampire kind of way.
The seals given in the Lesser Key are, essentially, the Proper Names of the fallen angels (within the greater Abrahamic tradition, of course).
For both of these, there are specific rituals involved in their creation and invocation, so the images themselves are rather inert.
HOWEVER … having said that, there is great power in Names. If you decided to tattoo the seal of Belial on yourself, and one day he happens to pass you on the street, it might just attract his attention. Think of it like this:
Think of the invocation ritual like calling your friend on the phone. There’s a procedure behind that; your mind is in the right state, as you make the conscious decision to get out your phone, and dial your friend’s phone number. If they answer, awesome! Now you’re chatting away.
On the other hand, let’s say you’re at the store while wearing a tee-shirt that has a random classmate’s face and full name on it, and they just randomly happen to be there too, and they pass by you. They notice the shirt, and stop. “Hey… that’s me…" they stop to say, "… why are you wearing a shirt with my face on it?" Suddenly you have their attention when you didn’t necessarily mean to, or even want to.
In short, if you want something because it’s aesthetically pleasing, my suggestion would be to use one of the Planetary Pentacles.