Change images and logo is quite simple you only need to replace the graphics with your own.
You will find the graphics on following locations:
- img/ico (all the icons)
- img/chat_now.png (for the slide up chat when online)
- img/contact_now.png (for the slide up chat when offline)
- img/faq_now.png (for the faq slide out)
- img/support_now.png (for the support slide out)
You should keep the dimension of each image.