An image is not a picture file that holds pretty pictures. It is a file that is the electronic copy of a CD-ROM.
This file is commonly called an ISO, as the most commonly used image file type is ISO. Other types include BIN/CUE, ISZ, etc.
The largest file a FAT32 drive can hold is 4GB. So you have to reformat the drive as NTFS. To do this:
1. Get all of your files off the flash drive.
2. Go to My Computer, right click the drive and click Format.
3. Under file system choose NTFS.
4. Format.