Customize Appearance

I could write a whole tutorial, but I don't have time right now (once 0.4 stable is out, then I'll write one :D).
So answering the questions:
1) For GNOME backgrounds (e.g. nautilus), copy and paste this file: ~/.gconf/desktop/gnome/background/%gconf.xml to /etc/skel/.gconf/desktop/gnome/background/. XFCE4 backgrounds are located here: ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-desktop.xml. LXDE backgrounds are a little trickier though, as there might be more than one LXDE profile, so go here: ~/.config/pcmanfm/ and copy and paste the profile directory to /etc/skel/.config/pcmanfm/
For 2 and 3, could you clarify a bit more? On 2, do you mean the spash on the livecd or on the installed system? And on 3, do you mean Usplash or Plymouth? And is it on the installed system or on the livecd?

On 2 on the live cd, absolutely.

For 3 same on the live cd and if you can tell us both for Plymouth and Usplash we wuld be happy!

Thank you very much for your input!

Okay. GRUB is actually not used because it does not support booting from a CD, and even if it did, it would be too heavyweight (relinux uses ISOLinux and VESAMenu instead). So the file you are interested in is /etc/relinux/relinux/isolinux/isolinux.cfg.vesamenu. Do not edit the "variables" though (i.e. the parts starting and ending in 2 underscores, __). I am not an expert on editing this file so if anyone could contribute a tutorial for this, it would be greatly appreciated :D

For question 3, I'm guessing you are talking about editing/switching themes, right? If so, this tutorial might help: http://www.ubuntugeek.com/quick-tipplymouth-themes-in-ubuntu-10-04-lucid-lynx.html

I'm sorry, due to lack of time and an unstable computer, I'll answer your usplash question later.

I'm very sorry for replying so late! I thought I had already clarified the usplash question too :/

I found a very good tutorial here: https://help.ubuntu.com/community/USplashCustomizationHowto . If you don't need to make a theme, follow steps 3-5 (or 4-5 if you already installed the theme) in "Dapper Usplash".

After a bit more googling, I found another excellent tutorial (that was somewhat easier to read), here: http://www.mediafire.com/?2yimyo3ow3t . Page 45 onwards of ubuntu_customization.pdf (inside the archive) explain how to make and install a usplash theme quite well.