There are 2 common mistakes when uploading customized images:
1) The names of the image files are incorrect. It is very important that the image files are named correctly as per our Installation Guide. The names of the image files are case sensitive, so make sure the images are named with “small caps” only. See the correct file names in our Installation Guides that comes along with our template / plugin packages.
2) The other common mistake is your images are saved in the wrong image format. Make sure the image files are in the correct format (jpg, png, or gif) as instructed in our Installation Guides.