Comment 4 for bug 1420859

You can download themes at deviantart.com for GTK3. You would then use the Gnome Tweak Tool or a command line gsettings call to change the theme.

Beyond that, though, I think Maxime needs to reconsider the method he has of creating alternating rows, since that functionality is now deprecated. Perhaps this functionality just goes away? Or there's some CSS code methods for alternate row theme that may or may not work.