Firstly here is an nice article explaining why latex is good .
Here are some editors available for latex:
For Linux :

• Kile : KDE Integrated LaTeX Environment
• Lyx
• Emacs : It’s available for a couple of operating systems like Linux, Unix and MS Windows. For LaTeX you should use the quite ingenious modes AUCTeX and RefTeX. You may refer my Emacs-page for further hints.

For windows :

• TexMaker
• LatexWide

Getting to grips with Latex
Getting Started with LaTeX
LaTeX Tutorial : some templates here
LaTeX Tips and Tricks

Creating image

1. Start the GIMP.
2. Click on File->New or type Ctrl+N
3. In the new image dialog, change Width to 640 pixels and Height to 480 pixels. (The image should be of size 640×480 pixels.) Now click OK.
4. Create the image which you would like to be the splash image. It’s quite fun to experiment with the various tools of the GIMP!
5. After you have finished creating the image, hit Alt+i or right click on the image and click on Image->Mode->Indexed…
6. In the Indexed Color Conversion dialog that appears, click on the radio button “Generate optimal Palette” and in “# of colors” enter 14. Click OK.(The image should be of only 14 colors)
7. Now right-click on the image and click on File->Save As…Save the file as ImageName.xpm in a directory of your choice.

You can also pickup an image and convert to required format by ImageMagik:

convert -resize 640x480 -colors 14 picture.jpg ImageName.xpm

Installing the Image

• gzip ImageName.xpm
• mount /boot
• mv ImageName.xpm.gz /boot/grub/

In the /boot/grub/grub.conf you have to point splashimage to newly created image i.e

# Splash Image
splashimage=(hd0,0)/grub/ImageName.xpm.gz

Now you just need to reboot !!

Here is my boot splash screen: I just added my name and Gentoo logo :

This is converted to jpeg. As blogger doesn’t support xpm images.

And some others :Some splash images

UPdated
For LILO you can refer to Lilo Boot splash