If your backgrounds are the correct size(s), then it may be that your file type is unsupported or it could be a technical bug, of which you would need to contact Episode (as @Alima.episode has stated). 
If your backgrounds are the correct size(s), then it may be that your file type is unsupported or it could be a technical bug, of which you would need to contact Episode (as @Alima.episode has stated).