I'm currently working actively on the Concrete icon set :)
Due to license incompatibilities though, and the actual progression of my work, I won't be releasing a complete gnome icon set anytime soon.
But I'll make it so, that it will be possible to easily include them into an existing icon theme. I'll be starting the conversions into the different sizes today, and it should be available either in the evening or tomorrow.
What will there be included ?
I think only mimetypes and basic folders , maybe a few emblems from 16x16 to 128x128 (more if requested, this is a vector work)
There's still a lot of work to be done on the devices, actions