I’m using this form to replace featured images and post title on my frontend form:

<form id="featured_upload" name="featured_upload" method="post" action="#" enctype="multipart/form-data">
<p><label for="title">Title</label><input type="text" id="title" value="<?php echo $post_to_edit->post_title; ?>" size="45" name="title" /></p>
<input type="file" name="my_image_upload" id="my_image_upload" multiple="false" required />
<p><input type="hidden" name="post_id" id="post_id" value="" /></p>
<?php wp_nonce_field( 'my_image_upload', 'my_image_upload_nonce' ); ?>
<input id="" name="" type="submit" value="Upload"/>
</form>

Here’s the saving process

// Check the nonce is valid, and the user can edit this post.
if ( isset( $_POST['my_image_upload_nonce'], $_POST['post_id'] ) 
    && wp_verify_nonce( $_POST['my_image_upload_nonce'], 'my_image_upload' )
    && current_user_can( 'manage_options', $_POST['post_id'] )) {

    //changing the post title
    if(!empty($_POST['title'])) {
    //$new_title = sanitize_title($_POST['title']);
    $new_slug = sanitize_title($_POST['title']);        
    $my_post = array('post_title' => $_POST['title'],'post_name'  => $new_slug);
    // Update new post title into the database
    wp_update_post( $my_post );

The problem:

I need the uploaded picture to be saved with the new post title ($_POST['title'])

Example:

The chosen image is image1.jpg

The new post name is renamed post (just like on $_POST['title'])

On the upload process, image1.jpg should be renamed to renamed-post.jpg