I swear I started a similar thread a while ago with the intent to post all maps I find.....
But yeah, it doesn't need to be a work of art or even anything beyond simple line drawing with basic features and names.
First time (awhile ago now) at a new site (ambush Botley) and they start talking about locations "yeah, but where is it?" - oh just follow someone....
By lunch we had a conversation with owner about it, we had done a very rough sketch of the rest of the afternoon by the end of the day, someone had found a dnd map maker and boom, a usable map was born.
The Gaol do theirs very well, with the "long game" locations, timings and scoring options all listed. Shout out to Justin as it hits 10Years in May.
CS used to hand a copy to all site first timers.
Many smaller sites might not need to bother, Red1 chiselhurst for example is compact enough to have have its areas clear and easy to navigate.
As is mentioned already, it doesn't need much.
For me, the effort of getting a map either on website or handed on game day speaks volumes about the sites level of welcome to new to site visitors. Excluding of course the smaller sites that don't need to...