Congratulations!
At last this idea is taken by someone who can draw!
There were some discussions on this already, but I would point to the one where my own opinions were stated:
http://forum.shrapnelgames.com/showthread.php?t=38342
There is also another thread currently active.
In short, I think that the EA nation should be mostly genie-based with human nomads as subject race, with MA being based on Khaliphate era (my own version was mostly based on 10th century) and LA on Osmanic Empire.
I agree about difference between city and Bedhuoin troops - you can look up how it was realised in my own attempt in the thread link above.
Considering magic and genies my own short research had shown that appropriate paths should include some Astral (astrology was relatively common, plus genies were often stated as knowing fate of people - plus Arabic folklore is the only place where I've seen something that could be characterized as teleport before 20th century authors). Another thing often mentioned, but mainly with female genies is turning people to animals, charm and production of food/wine - all from Nature path in Dominions. What I decided about this also can be found in the thread above.
As for your graphics - while I myself am not good enough at pixel art (which has already stopped 2 projects), I think yours are good. And I do not think that you should necessarily use an existing tradition of depicting horses in action as rearing. Another thing - Arabs didn't use composite bows like Turks or Mongolians. Their bows were better than common Western design, but not by much, and they didn't particularly like shooting warfare - maybe because of the risk to horses. What they should certainly have is light lancers with very fast horses - which could be deadly at first strike... Later they began to employ a northern Turkish nomads specifically as mounted archers - but those were most often relatively heavy troops (by the way, in Dominions these should be people related to those which conquered Tien Chi in LA, but no name for them is officially given
)... If you agree with the general concept I propose or have further questions - I am ready to answer and/or provide some content (as are possibly those who took part in previous discussion
).
So, please continue your good work - twenty centuries are looking at you!