Changing wallpaper and others of Live image

I've succeeded on creating Live USB using live build and guide. But I could not change default wallpaper and run some service on boot. I tried to add hook script, not succeeded. Also tried with live config scripts, but I confused with naming of the script. I did not find any guide for sequence number that should be included in script name. I've installed Cisco VPN client and want make /etc/init.d/vpnagentd service running when I boot the Live image. Additionally, want to change the default wallpaper. How can I do this?

Have you seen the following blog post? http://www.offensive-security.com/ka...linux-recipes/
Script: https://github.com/offensive-securit...p10-nonroot.sh

Thank you g0tmi1k, it was really helpful :)

Also tried with live config scripts, but I confused with naming of the script. I did not find any guide for sequence number that should be included in script name. I've installed Cisco VPN client and want make /etc/init.d/vpnagentd service running when I boot the Live image. Additionally, want to change the default wallpaper.