Picturesque meant - he decided after careful observation of the scenerey that inspired Twoflower to use the word - that the landscape was horribly precipitous.  Quaint, when used to describe the occasional village through which they passed, meant fever-ridden and tumbledown.
Twoflower was a tourist, the first ever seen on the discworld.  Tourist, Rincewind had decided, mean 'idiot'.

'It's happened at last,' he moaned.  'I'm going out of my mind.'
Good idea said the voice.  It's getting crowded in here

Rincewind shivered.  He was not, of course, an atheist; on the Disc the gods dealt severely with atheists.  On the few occasions when he had some spare change he had always made a point of dropping a few coppers into a temple coffer, somewhere, on the principle that a man needed all the friends he could get.  But usually he didn't bother the Gods, and he hoped the Gods wouldn't bother him.  Life was quite complicated enough.