It would save a great deal of re-pathing and inter-user coordination if the images used for custom decals and materials could be imported into the Revit file instead of just linked. The file format clearly can accommodate arbitrarily large raster images -- renderings, for instance -- and import images for other uses, so what's the problem?
In my own circumstance as an educator, this lack of functionality makes accepting student assignments without access to cloud file-sharing very problematic - students can't just submit the Revit model, but must remember to send any custom images as well, which I then need to unZIP and re-path for each submittal of each assignment.