i use the old photobucket plugin from 3.6 works great for 3.8
and im running it on my site atm, dont like imagashack thingy.
but there is a few mods out there that does this, but they dont make use
of the attachment system unless you actually upload the file to the server
which is proberly what your trying to prevent right ?
I recommend using that, theres also another similar mod just not happy about it.
Photobucket plugin