Just upload them onto your iDisk into a folder and use the following link structure...

"http://homepage.mac.com/*.macmembername*/.Pictures/*folderyouputthemin*/*nameofpicture.jpg*"

Easy as pie. Obviously replace the items in * * with those which they correspond to.

The vital part of this link being the dot before the folder, this tells the .Mac server that your looking for a file/folder in your iDisk...