An update on this topic has been posted on 2020-10-17.
The possibility to easily share plugins with other users and discover plugins written by other community members has been a powerful feature of QGIS for many years.
The QGIS Resources Sharing plugin is meant to enable the same sharing for map design resources. It allows you to share collections of resources, including but not limited to SVGs, symbols, styles, color ramps, and processing scripts.
Using the Resource Sharing plugin is like using the Plugin Manager. Once installed, you are presented with a list of available resource collections for download. You will find that there are already some really nice collections, including nautical symbols, Mapbox Maki Icons, and my Google-like OSM road style.
By pressing Install, the resource collection is downloaded and you can have a look at the content using the Open folder button. In case of the Mapbox Maki Icon collection, it contains a folder of SVGs:
Using the new icons is as simple as opening the layer styling settings and selecting the Mapbox Maki Icons collection in the SVG group list:
Similarly, if you download the OSM Spatialite Googlemaps collection, its road line symbols are added to your existing list of available line symbols:
By pressing the Open Library button, you get to the Style Manager where you can browse through all installed symbols and delete, rename, or categorize them.
The Resource Sharing plugin was developed by Akbar Gumbira during this year’s Google Summer of Code. The full documentation, including instructions for how to share your own symbols with the community, is available at www.akbargumbira.com/qgis_resources_sharing.