WordPress offers six different roles ranging from Super Admin to Subscriber. There is one role that permits a user to write and manage their own posts but cannot publish them; that is the contributor. Writing a post and submitting it for approval to publish without images is as easy as it gets. Posts of that nature are rare and can get a little boring. Images help make a post more interesting.

However, as a contributor, images cannot be uploaded with the post. A number of work-a-rounds may be put into place to remedy this, but each can be a time-consuming and often repeated effort. This may not be so bad for a short post, but one with many images can be more challenging than the effort is worth.

To allow contributors to upload images with posts would greatly simplify this. One site offers a snippet of code to add to the theme’s functions.php file.

if ( current_user_can('contributor') && !current_user_can('upload_files') )
add_action('admin_init', 'allow_contributor_uploads');

function allow_contributor_uploads() {
$contributor = get_role('contributor');
$contributor->add_cap('upload_files');
}

This has been tested as working using WordPress 3.9.1. Here is an after and before screenshot of the admin board of a contributor. Notice the image on the left has a Media option.

A contributor may now upload their post with images ready for someone else to Publish. After a successful upload, from the Media option take note of a couple of differences between images submitted by the contributor and images submitted by others.

This is an image submitted by anyone other than the contributor. Notice that the contributor may only view the image and no other action may be taken.

This image has a box next to it to allow for bulk actions. The contributor may also Edit or Delete Permanently their own image as well as view it.

A second contributor account was created to verify that another contributor may only view other contributor images as well as any other image and may perform other actions on own images. The results were as expected.

It is important to note that even if the code is removed from the functions.php file, the contributor role will still have the capability to upload content. This capability is persistent until explicitly revoked. The setting is saved to the database. To explicitly revoke this capability simply reverse the action editing the code above and append to the functions.php file.

if ( current_user_can('contributor') && current_user_can('upload_files') )
add_action('admin_init', 'remove_contributor_uploads');

function remove_contributor_uploads() {
$contributor = get_role('contributor');
$contributor->remove_cap('upload_files');
}

Although the functions.php may be modified with either of the pieces of code provided above, a cleaner and more portable method would be the use of custom plugins. One plugin to enable uploads and another to disable them. That could be the topic of my next article…

Source(s)
https://codex.wordpress.org/Roles_and_Capabilities
https://www.trickspanda.com/2014/01/allow-contributors-upload-images-wordpress/
https://codex.wordpress.org/Function_Reference/add_cap