The standardization team is currently working on the Wikimedia User Interface style guide, where it will be a one-stop shop for all design resources and specs in the future. But for now, you can obtain these updated resources from the Design Resources section of our team's wiki

It includes:

UI elements for use by designers / others (Sketch
•
how to use gif
) and
specs for
developers (WMFLabs •
LESS file);
Three ways of using our icon library -- SVG, SVG sprite, and Icon font.

We will keep updating this thread as more resources become available and updated.