can we use steppe portrait for mordvin and mongol?
You can, although it would be wholly inappropriate. Mongol in particular. The hats are kinda unique to the peoples of Desht-i-Kipchak. I may actually do an update to the Mongol clothing because I find them to be very inaccurate and I have already recreated around 20-30 articles of Mongol clothing in MD3 and Max just in case I needed them.
So basically medieval cuman cowboys? I can live with that
And sheepherders. They did ride horses from basically birth, but they had large flocks of sheep (like the Karakul sheep comprising the Phyrgian cap on one of the "common" male hats above) and cattle (which they tended to trade to the Rus). I would say their herds of livestock are much larger.
Anyways, the women wore some goofy-looking stuff. My first round was a little more all-encompassing. But, since the official Turks are based on the ones from the Ustyurt to Tien Shan and southwards, I can focus the Cumans a little more to apply a good level of Turkish variety. I may do the Pechenegs, are least with the headgear, but I have other plans before I really focus on that.
I'm glad you used S.A. Pletneva's studies while creating these pices of arts

Thumbs up!
How about Pecheneg ensemble? I read somewhere their nobles prefered Iranian suits, while lowborns wore caps of fleece and waistcoats made of leather.
Pletneva is invaluable, but there are others like Pritsak who were also useful. I've mentioned before, but I did have help with the research: One being a historical fashion student living in Russia who was an exchange student at my high school (who helped provide search terms and sites in Russian for me) and the other being an actual historian/archaeologist (who suggested books and other professional contacts for questions). Without them, I would certainly be lost, haha.
As to the Pecheneg's clothing, the Iranian "suits" were pretty much the standard riding gear for a while. The Byzantines adopted a version of it sometime after Justinian when they began to move away from "Classical" wear. The Turkic tribes also used them in various forms for thousands of years. And the basic gist is an outer-garment (kaftan, qaba', divestesion (?), khalat, yalma) with a right-over-left cross if the material did cross or was double-breasted. The "waistcoat" idea was more common amongst the Vlachs, who would even wear them with fur on the outside. They did like to wear felt, fur, and fleece caps. They stopped really utilizing the Central Asian
boerk style of cap, which is a felt, fur, or fleece "bowl" with flaps that could be turned up (e.g. the "Cuman Cap", sometimes with a metal or wood framework on the inside or even made with silk).
For more info, I would recommend Yedida Kalfon-Stillman's book, the databases of Encyclopedia Iranica, the Etymological Dictionary of Pre-13th Century Turkish, Persian
min'ai paintings, the
Varqah wa Gulshah, and just about any assessment of a kurgan stelae (like the Filatovka burial). Sadly, recreations are not as prevalent, and the availability of resources in English is difficult, but if you have knowledge of Russian or you can translate the Google translate you can make do pretty well.
Also, I would recommend doing an inter-library loan or using Worldcat or JSTOR to find comprehensive works on Byzantine, Persian, Mesopotamian, or Central Asian art. You can find a lot of info there, especially perusing margin notes.
show us new pictures
Wish I could. I spent the weekend taking my wife and in-laws to an amusement park, and then finished with some Cards Against Humanity and Settlers of Catan. I'll do more work this week and hopefully get a release ready sometime within the next two weeks.