Yes:
Go to "User CP" (top task bar)
Click on "edit signature" (in left "control panel, settings & options column")
Add photo in block and save, etc. You can also add a text message.
Notes:
1. I think there are size limitations for the photo.
2. When you do a reply the "Show your signature" in "Additional Options" (which is below the box that you are typing your reply in) must be checked.