Quote:
GRUB 2 can use PNG, JPG/JPEG and TGA images for the background. The image must meet the following specifications:
JPG/JPEG images must be 8-bit (256 color)
Images should be non-indexed, RGB
By default, if desktop-base package is installed, images conforming to the above specification will be located in /usr/share/images/desktop-base/ directory.
Photo can be JPG so that has nothing to do with it. But if it has converted and is not 256/8 bit then that's probably the problem. The photo is black and white so if the text is any other colour you would see it somewhere I'd say.