One issue encountered frequently, is the difference between RGB and CMYK. If you're unfamiliar with these terms, please refer to our Glossary of Terms in the column on the left. It will help explain the difference. Everything that runs through the printing process goes throgh as CMYK.
Another issue is that what you see on your monitor screen may not be the way it will appear on your printed piece. Camera settings can be set differently, the image can be viewed differently, and lighting in the office can certainly affect the way the images are viewed.