I'm sure this has been discussed before but music/sound support would be really neat to see in sketchfab. I'm working on quite a realistic face that I plan to animate and upload onto sketchfab. It'll probably just be an idle animation with the head turning and looking around, blinking. It's of a certain character that happens to have lines in movies, I thought what would be cool is if the head spoke it's lines as the animation is being played.
I'll probably bake a realistic render onto the texture then add a slight realtime shadow to the model, ignoring sketchfab's materials and end up with something that looks like a rendered picture instead of a game model. Bake the hair physics as the character changes his facial expressions and turns his head around. If done correctly a voice would really sell it I think, just a suggestion.