Nolan Chou

Sometimes we forgot change our file to a available name. So the plugin can help you auto change your upload file. 
I will add a filetype option of setting in next version. 
And a rename popup before the file upload if you change setting in future, default value is post_name.

wp_upload_rename

Change upload filename to random characters / random numbers / date / other by yourself.

dpoakaspine

Disallows PNG files. Usefor for multi-user environments with restrictive file settings and performance oriented sites.

Disallow PNG

Disallows PNG files. Usefor for multi-user environments with restrictive file settings and performance oriented sites.

wp_upload_rename vs Disallow PNG