I doubt that the Great Beings placed the design in the hands of the Skrall, because why would they give up the layout of their quite impenetrable fortress to a band of warlike beings who might try to invade the maze. I also doubt that some Skrall managed to map the place, because that maze is pretty hard to get through. I personally think that the maze design is just supposed to give the impression of the maze, and that in the Skrall culture it could represent power, or wisdom, or bravery, or something. As we have seen the Skrall have a very strict social order that is set around the glory of battle and similar concepts, so I think it would be plausible that the Skrall adopted the Symbol and incorporated it into their culture just because to them it represents something significant. And as long as it represents something significant they are going to continue to put it on there shields, no matter how hard they are to make, because just like with us humans if you give something meaning, people will hang onto it. If the design represents anything that I mentioned above, or anything similar, then I suspect the Skrall would do the same as us.