In addition to user waypoints and user map layers, ForeFlight now allows you to import User Charts that you can manage and display on the map.
The User Charts feature supports MBTiles, an open source file format developed by MapBox that allows for efficient compression and distribution of large charts. The feature does not yet support vector charts, which can also use the .mbtiles extension. A great tool for creating your own MBtiles is MapTiler, which is free to download and allows you to quickly georeference and export raster charts.