If you check the map at the Penny Lane sim you’ll see a flying saucer – right above the section of town with an alien crash landing. Next to it, in Scribzy’s Junkyard, you’ll see a zombie, though that will probably change into something else soon.
Scribzy Daxter, my friend, and neighbor created these images specifically to appear on the SL map. He made the flying saucer for me as a gift (it’s awesome, thank you!) and may sell map images similar to these in the future.
If you own land, a cool picture can make it more interesting on the map at least, so I’ll let you know when Scribzy has something for the public.