I believe the technology is available, already, even if it is a two step process import then re-export. The drop mechanisium can be designed and a drop zone defined to do what ever we want, perhaps dropping images in the images folder below the wiki then drag the filename into tiddlywiki to create a tiddler referencing an image by that name is already possible.
Of course I would prefer to drop any image in my wiki and create a tiddler referencing that image externaly wherever it came from relative or absolute antwhere in my desktop so I could organise my 100k+ photos. Only loading the image when its tiddler is opened or transcluded.
Regards
Tony