Before upgrading to version 6.53 power user were allowed to modify and replace images in the image library without needing approval for publishing. After upgrading to 6.53 power user can add new images and are not required to have approval to publish. But if they edit the same image and change the picture, they are now required to have approval to publish.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch. This issue was resolved in the latest version of Blackbaud NetCommunity