All images must be 8 MB or smaller. If they are too large they will not upload at all, if they are too small it will not be a good image.  8 MB have a resolution of 1600 x 1200. If the photos are larger than this they will not upload. 

Please also avoid uploading photos that are smaller than 600 x 400 as these will not look good on the website.  Do you want to see the difference?

Here is a photo found on Wikipedia that has a low resolution: 300 x 201 The photo is a little blurry.  If I make the photo any larger it will be very blurry. 

This photo was taken at the 8 MB range 1600 x 1200 You can see how clear and crisp the image is.