ha! tradition! thanks, Pix!
heres my firrst(?) contribution:
alphacentury + alphabrush terrain, starry night customized material (see below zipfile including a script showing one tip for how-to-use), as a ghost wont have a shadow i didnt need to think about bg depth - so the terrainpic was imported as a texture into a new resized canvas; the ghost was made from sweep profile, standard (mask all - col) and handpainted mask combined were used in an attempt to make the folds ghost was made on own layer, its materials transparency tweeked higher and flatten layer was switched off after a first best render. rendering in a layer of its own allowed both transparency to show and me to play with render-antialiasing settings without affecting the whole image - i think i never rendered anything at highest super sample settings - but with flatten layers off it helped to get rid of the heavy sweep profile jaggyness without blurring the background (image is original-size, no additional resize AAing).
hope you like + have a fantabulous and halloween 03, everybody!
ghostscript huge file (2mb - thanks, Digits for webspace!!!) including ghosttool, -material, -light - you might want to abort the script after loading these, nada interesting following
edit as per next day: lol, Flycatcher re your below comment - i assume there might be people who think the kind of device you are thinking about is creating a myriad of ghosts when they are used the proper way
as i thought it looked too deserted i have added a layer with bats (made via alphaskin based on a batshaped i took from the web)