Is your image big enough?
Summary - images in print are 1/4 the size of images on screen. Make sure your images are big enough at 300 dots per inch
Facebook photos will not do. Because of the size of the dots used on the screen and used for printing, images to be printed need to be 4 times the height and width (16 times the size!) to look as good printed as they do on screen.
To demonstrate: Here are two photos of a peacock.
The first:

Ok, so it's a little out of focus, but those birds move fast! Aside from that, the image is crisp, and looks ok. However, if you print it out:

Oh dear...
So what do you need to do about this? Well, if you are just sending us photos, please send the original photo you took, rather than just a small version from Facebook. If the image is printed at three by five inches, the resolution will need to be 1500 by 900 pixels. By contrast, the average Facebook image is a mere 600 by 450 pixels. Tiny!
How to check
If the image is on a website somewhere, you can check the resolution (in Firefox at least) by right clicking and selecting properties. If it is on your computer, then on Windows, right click on the file, select properties and it should be on the Details tab. On a Mac, right click, Get Info, and it's in there somewhere :)
