4 examples. Take 1 of these images, save it then try to upload to a xenforo board.
http://www.p8ntballer-forums.com/bon/landscape1.jpg
http://www.p8ntballer-forums.com/bon/landscape2.jpg
http://www.p8ntballer-forums.com/bon/landscape3.jpg
http://www.p8ntballer-forums.com/bon/landscape4.jpg
It seems that the attachment handler cannot cope with such large images, so just bombs out
http://www.p8ntballer-forums.com/bon/landscape1.jpg
http://www.p8ntballer-forums.com/bon/landscape2.jpg
http://www.p8ntballer-forums.com/bon/landscape3.jpg
http://www.p8ntballer-forums.com/bon/landscape4.jpg
It seems that the attachment handler cannot cope with such large images, so just bombs out