When I turn off Settings / Widgets/HUD / Show Clock and Settings / Widgets/HUD / Show Weather Forecast and Settings / Widgets/HUD / Show EXIF in Slideshow and Settings / Widgets/HUD / Show photo file name, all bottom widgets will disappear and there is nothing obscuring the photo. Could you please try turning off all of the abovementioned settings?
Thanks for letting me know, great that we managed to solve this issue. I think the "Show Picture Only" setting would duplicate the effect of disabling all of the widgets, so I'm hesitant to implement that. Instead I propose to document this in the http://www.android-photo-frame.eu/faq.html