actually, as usual, spoke too soon.. Just found out how it can be done..
dcop kdesktop KBackgroundIface setWallpaper %u 6
.. that as I understand will send in konqueror the signal to set a selected image as the background. So, id decipher that its this kdesktop that needs to be running.. *sigh* .. sounds big and clunky..
Well, I had a go at it.. launching just kdesktop gives me my kde wallpapers and icons, plus fixes the transparency.. But as usual with KDE, draws are slow enough for the eye to catch a glimpse of unfinished work, and as I said, clunky..
edit: also noticed that running kdesktop takes away the fluxbox menu and makes things more clunky, this is not a solution.
If anyone fancys writing a dcop wrapper that will emulate the wallpaper interface and send the rest to the real dcop, id be most thrilled to try it out.. (; ... Unless there is some real way to get around this..