So now after two years since the last post, are there any solutions yet to see whether the current usage of those GPU mining rigs can also be setup to use for 3D rendering like setup? 
Could be but I don't know of any. Problem is, even if there was some, very likely they'd only need to use your cards for just a few hours at a time. And rendering usually comes with big filesizes not just tiny hashes so GPU mining rigs might require lots of disk space and high bandwidth connections. Profesisonal rendering or other professional uses of GPU arrays might also require secrecy and they might just invest the money into GPUs as well.
Anyway, I'm hoping something will pop up but it's hard to imagine that whatever would come up, it wouldn't be instantly oversaturated by all the GPU miners, essentially bringing down the profits to mining levels - which are not great these days.
