It looks better now. 

Thanks for the response. 

I was a little worried I'd make the sphere too shiny if I put too much shading on it, but it definitely does look different compared to the rest of the wall, so I'll probably go back and add some more shading to it, maybe just one more tone for the highlights. 

I feel like the shading on the sphere is imcomplete (missing?) compared to the rest.

It looks good though!