Most serene - mountain peaks, regardless where you are either Storm peaks, IronForge, Skyrange, Shrine of Friendship, Kun Lai Summit
Most chaotic/ugly - where ever there are tiny shas and undead/scourge (yes, the undead had turned Southshore into a chaotic place with those green gassy chemical carts)
Architecturally beautiful - Dalaran, elven cities (high, night and blood) including places in Outlands, Stormwind
Naturally beautiful - Zangarmarsh, Vashjr, Nagrand (dull places but beyond the creatures and quests, they are actually beautiful)

Well, Thunderbluff is actually based on the red indian concept of culture, you basically see totems, tents/tepees almost everywhere in thunderbluff and mulgore, kampung it might be but it is also the most serene and nature friendly of all the Horde cities.

Loch Modan tho, is a very disturbing place after Neltharion clawed his way out of the earth core. the lake's water is dried up, dam is broken, the same also goes to darkshore, both used to be quite interesting places.