When you display an image in a GuiMLTextCtrl and the client does not have that image, Graal does not refresh/reflow that GuiMLTextCtrl after the image has been downloaded, so the image is not displayed until that Gui ctrl is pushed back onto the display or reflown manually.
(<img src=example.png> in GuiMLTextCtrl contents)
Of course you can work around this with a download system, but I feel it would be more appropriate to make GuiMLTextCtrls either wait until the image data is accessible, or reflow when the image is available.