The filepaths will be in the <EffectDB> section. Look for ones that begin with E_CHECKBOX_Pictures. It will look like this line I pasted blow where my filepath is C:\xLights\2015\Christmas\StarWarsImages\.
<Effect>E_CHECKBOX_Pictures_PixelOffsets=0,E_CHECKBOX_Pictures_WrapX=0,E_CHOICE_Pictures_Direction=none,E_FILEPICKER_Pictures_Filename=C:\xLights\2015\Christmas\StarWarsImages\Blueman landed.gif,E_SLIDER_PicturesXC=0,E_SLIDER_PicturesYC=0,E_TEXTCTRL_Pictures_FrameRateAdj=1.0,E_TEXTCTRL_Pictures_Speed=1.0,T_CHECKBOX_LayerMorph=0,T_CHECKBOX_OverlayBkg=0,T_CHOICE_LayerMethod=Normal,T_SLIDER_EffectLayerMix=0,T_TEXTCTRL_Fadein=0.00,T_TEXTCTRL_Fadeout=0.00</Effect>