I get this as well with some images. It seems to only be for the images hosted on here, images hosted on photobucket etc generally show ok.
I think it's just one of the foibles of tapatalk to be honest, and there is no fix as far as I'm aware (other than perhaps updating the tapatalk software at the server side if it's not upto date).
Before Farjo gets here and says it : did you know foc-u now has its own dedicated mobile theme? Check it out, all the images show ok on there