Using the BBcodes I am sure you can do it like this
Using the Square bracket [ ]typethe word IMG between the open and close brackets, enter the link to the imagine. thenat the endof the link you have to add the square brackets again with /IMG in between them
I put this between the IMG code and hey presto..... there you go.
The quick answer to that is no.
You need to upload the photo so the forum can see it.
If the forum had it's own photo section that you could link to it.
Photobucket is ok for these forums and I use it for all my hosting but not for my personal and treasured photo's!