what framework do you use for your theme-panel?
You need to make image upload into your theme panel page and a line of code to call it everywhere of your theme you want.
This is an example:
in theme panel function page
$options[] = array(
'name' => __('Introduction Image', 'options_check'),
'desc' => __('This is your site logo.', 'options_check'),
'id' => 'introtext_uploader',
'type' => 'upload');
and into your theme e.g header.php
<img src="https://wordpress.stackexchange.com/questions/189397/<?php echo of_get_option("introtext_uploader'); ?>" alt="" />