Remove the text if you want.
Start making the picture that you want in Notepad2 or Notepad++.
See the section "What is the DISPLAY File Format?" on
for more information about how to make coloured text.
Search also for "Notepad2" in my post on
It explains how you can add colors to the text easily, without to use a hex editor.
Remaster the iso.
Download some Virtual Machine (qemu, Virtualbox, VMware Virtual PC,...) and install it.
Point your virtual machine to the iso file and let the virtual machine boot from the cd.
Now you can see how your picture looks.