I hope by now you have solved your issues.
You should convert your pics to png format which would make the white transparent.
Then import that one and it will solve most problems. If it still exist then go into the background options and choose color and then select your prefered choice then hit ok this will solve the rest of the problems of this kind. You can choose the same color as the original background as the choice for background color and problem is solved.
Finally if you must use the jpg and can not convert them to png then when you are erasing the background zoom in until you can see the individual square pixels then erase the ones at the outline of your pic this will get rid of the ghost effect you are having.