The website limits the size of pictures that can be uploaded. There are pixel size limits and there are size limits on the file size. You may need to "shrink" the size of your pictures.
If you can't manage to do that with your software, you can email the photos to me and I will shrink them for you and then email them back to you. If you need to email them to me, send them to: firstname.lastname@example.org I can resize them and email them back.