The heaviest armor that the Muslim troops should wear should be guard helmets and lamellar armor. The Kataphract horse from the Hugemod with it's lamellar style plating would be perfect for the Mamluk Khassaki (the elite horse troops of the Mamluk armies).
Low level Muslim soldiers should have headcloths and coarse tunics, light should have nomad armor and nomad caps/steppe caps, medium level ones should have Padded Armor or chain hauberks, spiked helmets, leather gloves, etc.
Weapons should be scimitars, fighting axes, hand axes, spears, lances, spiked maces, nomad sabres, glaives, and any specialist weapons you guys would like to make.
All Muslim men should be wearing facial hair, as it was and still is considered pious to have facial hair in Islam.
Muslims not wearing shirts would be immodest and totally out of the question. When you are in a hot desert climate you need robes of some type to keep the sun from directly hitting your skin, usually sandy colored or white. Muslim warriors often wore brightly colored clothing along with their armor and weapons. It is also considered pious for Muslim men to wear some kind of covering over their head, like a turban, headcloth, those little beanies you see modern ones wearing here in the US, etc.
Here are some pictures to give you a few examples:
I would also recommend you replace the Dark Knights with Mongolian War Parties, and the Khergit Raiders with Mongol Raiders. Whichever side you choose to be the Muslims, like say the Vaegirs, their deserters should be changed into the Hashishin. That's just my two cents.