I use 1.3 and React, many React packages on NPM have their own CSS files. Usually they will be somewhere in the node_modules directory (for example package/dist/css/). It’s not the biggest problem, you can just copy them to a directory outside node_modules and Meteor will be able to detect them.
It will straight forward crash Meteor. I have asked the author of the package and I’ve got this response:
But if you use webpack or browserify to build your app. There are css loader plugins to handle this special kind of require. (…) I never use Meteor before. I think maybe there’s some css require plugin in Meteor too.
In Meteor 1.3 you can require css files in JS, they will be attached to the <head> for now, but I gues this will not work in this case and I wonder if this will work when you want to require from node_modules at all. We need to wait for Meteor 1.3.1 (I hope).