Setting Rules:

Here are some setting rules I've been toying with. I've tried to use what Savage World's has in terms of rules in order to produce the various flavors of the Classic Dark Sun I remember from when I started gaming in Junior High School.

Weapons of Bone, Stone, or Obsidian*: -1 to Attack and Damage
*If the wielder of a bone or stone weapon rolls a 1 on his Fighting die, no matter the end result of the attack, he must make an successful Agility test or his weapon breaks at the end of his turn (Meaning he could use the weapon twice if he has the Frenzy Feat, even if it breaks on the first attack). These include: Axes, Flails, Swords
Safe Weapons: Bows, Crossbows, Club, all Crossbows, daggers, quarterstaff, sling, all Maces, net, all spears, and whip.

SW:EX Armors Translated to Athasian Materials
Plate Armor: Mekillot Hide
Chain Hauberk: Shell-Armor (chitin and giant hair), Cord-Armor
Leather: Arpig Leathers
Reinforced Leather: Leather w/ Rivets of Bone or Hardwood
Reinforced Chain: Chitin Plates

Weapons of Steel vs. Armor
Athasian armor is not made to defend against weapons of metal, as its unusual to encounter an iron or steel longsword on the field of battle or in the arena. In game terms, weapons of metal are treated as AP +1 when pitted against Athasian-made armor. This stacks with other AP bonuses from magic, gladiatorial Edges, etc.

The Written Word
In the Tablelands and other places, literacy is banned or taboo among the common folk. To read is to be a wizard, and to be a wizard is to dangle at the end of a rope. Therefore all starting characters have the Illiterate (Minor) Hindrance. There are two ways to counteract this problem during character creation: the first is to take the Edge: Noble, which grants literacy in addition to its other powers and responsibilities. You may also take a Free d6 in Knowledge (literacy)--this is the option best suited for wizards. Any characters that choose to remain illiterate during character creation are entitled to a Free d6 is a skill associated with their homeland (see below). Any character can gain Knowledge (literacy) during the course of the game; d4 indicates familiarity with one’s native language, d6 indicates familiarity with all other languages of which one has knowledge.

Regional Skill Bonuses (Take this if You Don't Opt for Literacy)
Tyr: Persuade d6
Raam: Streetwise d6
Draj: Intimidate d6
Nibenay: Stealth d6
Urik: Fighting d6
Glug: Survival d6
Balic: Sailing d6
Ringing Mtns: Tracking d6

"Telepathic" Trappings (as per the major and minor trappings in the Fantasy Companion)
Offensive (Minor): Psionic Attacks that hit with a Raise result in a -2 to all Smarts-based skill rolls, including Psionics. (until the power subsides or the victim is no longer Shaken).
Offensive (Major): Reduce the damage by one die level on spells such as Bolt, Jet, and Blast and the user can elect to sap Psionic Power Points from the victim rather than Damage.
Defense (Minor): Instead of adding to Defense levels, Psionic powers that earn a Raise fine-tune the user’s psychic senses, making it impossible for an enemy to get The Drop on him for the power's duration.
Defense (Major): When applied to powers such as Armor and Deflection the effects are doubled, but the Powers only function against Psionic Attacks.

AB: The Way
Limitations: Drawn from one’s own mental strength, psionic powers are not transferable to others. Whereas a wizard can grant Armor to herself or an ally, a psionicist can only use such a power on himself*.
Benefits: On the plus side however, Athaisans have been studying The Way for millennia, leading to a more efficient use of mental energy (i.e. more Power Points).
Starting Powers: 3
Starting Power Points: 15

*I lifted this idea from toadpooka's Savage Sun conversion. I think it's a great idea that makes sense in light of the setting's reliance on Psionics as a core fantasy element.