BuddyPress.org

@kmp2

You can use the following code snippet to increase image dimension.

function wbcom_custom_cover_image_sizes( $settings = array() ) {
    $settings['width']  = 1920; // Your desired width
    $settings['height'] = 1080; // Your desired height

    return $settings;
}
add_filter( 'bp_before_xprofile_cover_image_settings_parse_args', 'wbcom_custom_cover_image_sizes', 10, 1 );
add_filter( 'bp_before_groups_cover_image_settings_parse_args', 'wbcom_custom_cover_image_sizes', 10, 1 );

You can also add custom CSS for cover images to make them responsive and adapt to different screen sizes.

you can check https://codex.buddypress.org/themes/buddypress-cover-images/ for more details