I had an issue with my WordPress edit image not working when I installed it myself on Centos. If you would like the ability to do advanced image editing in WordPress when running on Amazon EC2 Linux you will need to make sure that you have installed the PHP GD libraries or none of the image editing capabilities will show up.

sudo yum install php-gd

After a lot of searching I found this great answer on Stack Overflow which pointed me in the right direction. Have added this step to my previous post for setting up WordPress as well.