Importing Assets during runtime

I am interested in Unity for my project.

I checked the Pipeline documentation, but I couldn't find anything about runtime imports of dynamic game assets. Essentially the game will create bitmap files, and import those bitmaps as well as custom user made bitmaps. Sounds easy enough but surprisingly its a commonly unsupported feature in most graphics engines I have come by. Especially ones with dedicated pipelines :/ .

you can load "PNG" and "JPG" images in runtime using WWW.texture.