I made roflbot a month ago and it's been neat to see various LJ image macro communities using it for pictures (my favorite so far: ihasatardis). I just updated roflbot with a customized mode for adding text to LJ userpics. If you type in your username, you'll get a selection screen for one of your userpics:
After you select a userpic, you can add text to it, move the text around with the mouse, then save the final image back to your LJ userpic list with just a couple clicks. No graphics program needed!