I really got to know and love sketchfab over the past weeks! It's an awesome idea with already a great and feature-rich browser application just as it is now!
But want it to grow even better so here's some stuff I'd love to see implemented. I don't have a lot of know how about browser tech so these are just pieces of my mind
It would be nice to have some more insight on how much a model is viewed (per day/ week) and where those views come from. Something like Google Analytics.
Since in every game engine nowadays you can create your own shaders I'd love to see that feature added to sketchfab. I understand there might be limitations due to browser tech but even with limitations I guess it would offer a lot of artistic potential.
Particle Effects: I know you're working on animation and in theory you could bake a particle based animation to keyframes. I'd still love to see a particle system implemented in the viewer if there's any way to do that. It could offer options like color-over-time animation, randomness and animated spritesheets.
Well, that's all!
Hope you consider it if there's any chance to realize some of it.
Looking forward to the shining future of Sketchfab and hope it'll become an all-known standard for viewing 3d models in all browsers.