change boot pictureHi the
 

Hi there :)
Myboot Loader is the grub... I need to know if it is possible to change the default image with a new one created by me!
Is is possible? What the format must be? What extension?
Are any documentations available?

Look in your /boot/grub folder for a .gz file, that file has an .xpm file in it that is the image that is shown when your grub boot menu comes up.

It is a read only file so you will need to temporarily make it writeable by root when you replace the image inside with your own image. You can view the file in an image viewer to see what it looks like and what the size and dimensions are.