Yes, but you have to link them from an uploaded image site, like photobucket. The you use the icon above the edit that looks like a globe sitting on top of a pair of glasses (goggles, an 8 on it's side, I am not sure what the heck that is). Or you can use the image tag, put img in brackets, put the link to the image, and then follow it with a /img in brackets.
When linking from sites, make sure you link from someplace you have an account, like photobucket. It's bad netiquette to link from someone else's website, especially if they pay for their bandwidth.