Well, no, I wouldn’t say that. Different gates are portals to different places. Usually places in some level of the collective astral, but some to higher dimensions.
The Gateway of Pacts, is not the same thing as a square for one of the Kingdoms of flame, is not the same thing as the portal in the Shadownomicon by D.H. Thorne. They’re all gates.
Here is another example of a gate created by former member Lady Eva:
As noted above, they are created by the mage that invented them. You can make your own too if you like.
Do they? Do you mean specific gates and you’re asking why they look similar? Can you post images?
The ones I mentioned above don’t look related… There are three gates in the Book of Azazel and none of them look the same either. Can you elaborate?