It is very nice thread, I have to give you the credit.
Thanks
Serbs (especially those who adopted orthodox Christianity) still use (celebrate) many things from pagan period that are shown on your picks. Someone already mentioned “slava” that you have in post above where you have a “lunch” (trpeza) with candles. Custom in the spring with flower coronets (usually on the. St.Georges day) and most important burning the trees or branches that is still in use on a Christmass day eve, either in front of churches or in homes. And everybody gather around. And the more sparkle the burning tree made it means more joy and happiness in that year. It is all a bit modified as Danubian Cossack said.
And actually the main reason why majority of serbs accepted east over west Christianity (and they could both since they where located where this two meet) was that east one was more flexible and west more rigid and Byzantine missionaries let people leave there own pagan custom and incorporate them into new adopted religion, opposite of westerners who where more strict. So it did stay until nowadays.
Well, it's would be really cool if there will be specific flavour events for each pagan faith, relating to holidays, rituals, etc.
And one more thing (question). Some of these Slavic people where in two places at the same time. Like Wends that you have it in west group but starching all the way to south. Or Serbs who partially came to Balkan peninsula and partly stayed in what is today east Germany. I know that they are two different nations today (one almost completely distinguish (and the other on the good way on the same path )), and thay are called different Sorbs, and Serbs, but they were the same at the time (and they still call themselves the same “Srbi”. Do you think that should be represented or not?
Well, yeah I thought of that. Sorbs -> Serbs, Dregovichi in Belarus and Draguviti in Macedonia, Severiane in East Ukraine and in South Bulgaria, Poliane in Poland and in Kiev etc. But since you guys say there's no need to fracture the South-Slavic tirbes further than simply Horutans/Croats/Serbs/Bulgars, this kinda answers the question. Sorbs were a part of Lusatian (Luzyca) confederation of tribes, so, imo there should be just a tribe named "Lusatians" in Wendish parts. And Southern Serbs will be Serbs, i.e. they will be two different tribes (perhaps both with Serbian as a culture). As for Polane in Poland, and Poliane in Kiev - despite the name, they weren't related, most likely. At least for the game purpuses, it's better leave them as two different tribes, since one was the basis for Poland, and the other - for the Southern Rus'.