Desert will definitely be useful for any normal atmosphere you will have while traveling.
So, camp + camp on fire - There is a Desert Camp set, and then Elements - Fire, of course. Screams of distressed people can be found in several sets - Attack on Sandpoint and Debauched Gala are two of them - the elements of “women screaming”, “thug roars”, “riotous yelling”, and “men’s cries” should get the chaos of the attack across.
For the abandoned temple, you might like Caravanserai (from the Dreams of the Yellow King set), as that is a stone building in the desert, abandoned. It also has some magical resonance and creepy elements and one-shots to play up the “eerie” factor of its abandonment. The gremlins could be represented by the Goblin Battle, stirges by Hell Swarm or Sci-Fi player’s Swarm Attack. Spider by Riot and Ruin’s (Black Stars Beckon) “leng spider battle” mood. Tiger Battle has monkey hoots for your baboons! Ooze Battle for your oozes.
The battle market might be best served by the set Slave Market of Okeno (from Whisper Out Of Time), specifically the “laughing fleshfair” mood. There are gnolls already in that set, but Gnoll Battle is always an option! The boar could be done by Heroes of Undarin 3 (Pathfinder Playtest 5), the “boar demon battle”, likely just using the boar demon grunts and flesh attacks and whatnot. That set also has battles for a toad demon and mutilation demon, so that should be plenty of demons to go around. The set Into the Valley has a Harpy Monk mood that should work for your harpy.
The being in the local temple, you don’t mention what it is, but there are sets for Ghouls, Wraiths, and Undead, if it is something of that ilk. If you need something more specific, let me know (or PM if you don’t want to post spoilers).
