Roku

This plugin makes uploaded files only accessible by logged-in users.

Uploads Protector

This plugin makes uploaded files only accessible by logged-in users.

Sean Butze

Many users do not compress or resize their images before uploading them into a post, and oftentimes WordPress’s maximum upload limit of 2MB-10MB is still too large to prevent the insertion of photos that can signficantly slow down a website.
WP Image Size Limit allows an administrator to set a custom file size limit that is specific to image files and smaller than WordPress’s general file size limit.
This is especially useful when you need to put tighter restriction on image uploads but want to preserve the ability to upload larger files of other formats (audio, video, etc.).

WP Image Size Limit

Just what I needed to tamp down those designers who think it's okay to use 20MB images!

Brilliant

Adds a new setting under Settings -> Media where an admin can set a maximum upload file size for image files.

Uploads Protector vs WP Image Size Limit