help me plz

hey, im having problems... half my members dont have a serva to upload there banner to, i cant figure out how to make it so that when they attach there banner to the forums they can put the img codes around it to use it in there sig, like heres an example:

this guy attached his banner to the forums heres the link http://www.ge-metal.com/forum/attach...p?s=&postid=56

once it was attached, he got the link from the attachment and edited his sig and put the img codes around it, but when he checked his sig, it was only a link, how do i get it so that attachments show up in the sig?