It's the type of picture you are trying to post. The ones you posted which are adjustable are the ones giving you trouble.
A member ( beekeeper ) posted regular pictures of his new pirogue seat after your private message to me. Just today he posted this one. viewtopic.php?f=11&t=10313&p=99705#p99705
I would suggest you contact beekeeper and see who he is using for his pictures since the system will accept them.