Lettering and straightforward designs can be converted into logos easily. A logo is made out of one or just a few solid fabric colours, so a more complex picture, such as a photo, would have to be simplified to design an effective logo.
Pictures are usually made up of individual pixels when saved using jpg, png and bmp file types. To cut a logo requires a different type of file which can be created using a pixel based image, but the conversion process can take time to do well.