Would be nice for the store to have a 3D-360 degrees product viewer. I will give customers the possibility to look at the object from all sides before buying. That provides much more information about the model than a 2D picture taken from just one view point.
You can leave it to creators to make their own 360 degree 'pictures', but it would be even more awesome, when you implement something for us to use, when we create our marketplace listings.
For example when I upload my model to the store, there is something simple like a button that says 'generate 3D view'. My model gets uploaded in the implemented 3D viewer. Then I have some limited options to adjust my model to the viewer, like I can change the size a little, move camera bit more to left or right, higher or lower. and I have possibility to set a starting point. That is the point of view that will be shown in the store by default.