What type of database are you connecting to?
Crystal is picky about images. It will NOT display .gif images, but it will display .jpg, .tiff, .bmp, and (I believe) .png images. If you're connecting to SQL Server, it likes Image fields. If you're connecting to other databases, it likes BLOB fields.
So, it depends on both the type of image and the type of field that it is stored in.
-Dell