On our recent visit to China, I kept noticing Chinese characters that seem to depict what they say. I think I'm right in saying that 'entrance' is written using characters that both look like and mean 'person' and 'gate' (literally, 'mouth', I was told).
But apparently it's just coincidence that the first character below looks like a toilet...
Here's the corresponding icon for Exit. Almost a new ideogram in itself.