Storing photos.....as in your backups, yes, but it would be safer, and faster, to use a USB or FireWire drive connected directly to your computer.
Storing photos, as in placing a "live" or "working" image library on the drive, not recommended.
The reason for this is that access to the drive is quite slow, much slower than connecting the drive directly to your Mac, and there is an increased danger of a momentary break or lag occurring between the photo application and library, which can corrupt the entire library.
This would be especially true if you were trying to use wireless on your computer.
For more information, you might want to post over in the iPhoto or Aperture areas to confirm.