I think its the facial expresions and weapons for the most part. And I converted all 85 of the models in my army similar to the ones above. I also chopped up quite a few of them to make my own plastic bestigors, since back then the only choice was metal bestigors.
That left me a lot of chopped up pieces and lead me to this. If you have a bitz box like mine, which is pretty much all chaos, you have plenty of capability to crossover.
Some of it works, some of it could be done a bit better. When I build I often build the army pieces first then figure out later what I want to do with the bases, learned this the from all of the Fantasy work.
Decided to leave the bulk of the gor tabards and buckles exposed and not take them off. If you look at the normal beastmen above those icons are just kind of drooping down around the waist.