Hi @maciejkunicki,
I have found a way to change the header image with the author gravatar on author archive pages, however, it looks stretched as the image within the page header is a background image, so its purpose is covering the entire section rather than being adjusted to look nice.
The only way I was able to achieve this was by editing the theme file,
hestia/inc/views/blog/class-hestia-header-layout-manager.php
On line 510 there is a function called render_header_background()
You can replace it with the following one
/**
* Render the header background div.
*/
private function render_header_background() {
$background_image = apply_filters( 'hestia_header_image_filter', $this->get_page_background() );
$customizer_background_image = get_background_image();
$header_filter_div = '<div class="header-filter';
$author_id = get_the_author_meta( 'ID' );
$author_profile_image_URL = get_avatar_url( $author_id );
/* Header Author Image */
if ( is_author() && $author_profile_image_URL ) {
$header_filter_div .= '" style="background-image: url(' . esc_url( $author_profile_image_URL ) . ');"';
/* Header Image */
} elseif ( ! empty( $background_image ) ) {
$header_filter_div .= '" style="background-image: url(' . esc_url( $background_image ) . ');"';
/* Gradient Color */
} elseif ( empty( $customizer_background_image ) ) {
$header_filter_div .= ' header-filter-gradient"';
/* Background Image */
} else {
$header_filter_div .= '"';
}
$header_filter_div .= '></div>';
echo apply_filters( 'hestia_header_wrapper_background_filter', $header_filter_div );
}
I hope this will help.