For that you can do it with this changes installed in a module:

In a .py

from openerp import models, field

class ext_website(models.Model):
    _inherit = "website"

    website_image = fields.Binary("Logo Image")

class website_config_settings(models.TransientModel):
    _inherit = 'website.config.settings'

    website_image = fields.Binary(related='website_id.website_image')

In an .xml

<record id="solt_view_website_config_settings" model="ir.ui.view">
    <field name="name">Website Soltein settings</field>
    <field name="model">website.config.settings</field>
    <field name="inherit_id" ref="website.view_website_config_settings"/> 
    <field name="arch" type="xml">
        <xpath expr="//div[@name='social_media']" position="before">
            <div>
                <group>
                    <field name="website_image"/>
                </group>
            </div>
        </xpath>
    </field>
</record>

<template id="layout_menu_header" inherit_id="website.layout_logo_show" name="Soltein Menu Header">
    <xpath expr="//img[@src='/logo.png']" position="replace">
        <img t-att-src="website.image_url(website, 'website_image', None)" t-att-alt="'Logo of %s' % res_company.name" t-att-title="res_company.name"/>
    </xpath>
</template>

Put all of this in a module and install it. This will create a binary field to store the logo image for the website, in the menu "/Settings/Configuration/Website Settings" you could add the image in the field with label "Logo Image". After that just reload the page to see the logo changed

Hope this helps

Yes i mean website, the logo you have a the top of the left colomn in odoo web portal, admin, and so on. I have difined the company logo, this one is displayed everywhere. I'm not in multi company config. I would have a different logo on my receipt ticket of my POS than the one defined as company logo.