Of course... how you feels about these animations may differ between people, but I did my best, so I wish someone who thinks this is nice can apply this usefully.
It's quite short animations but it takes almost 6 hours cause I didn't buy Photoshop....
so I draw this with MsPrint, and some fundamental utilities
bootanimation.zip (letter 'G' appears, then keeps glowing)
shutdownanimation_rev.zip (letter 'G' turns brighter, then shatters into pieces)
(hmm... gif animations are playing so slow in my computer... if you are, too, remember that animation goes faster than you see above.)
In Korean JB rom, it's easy to change boot/shutdown animations : just paste these animation zip files to directory '/system/media/'.
But I don't exactly know about other roms, so you might have to convert these files to other format, or even decompile some apps.
I don't mind whether you use images inside these animations, but please tell me after using them : as I mentioned, they're 6-hour-images
2013. 1. 30. : I improved some brightness problem on the first uploaded file(shutdownanimation.zip), and it is uploaded now(shutdownanimation_rev.zip). When you apply this shutdown animation, please rename "shutdownanimation_rev.zip" to "shutdownanimation.zip"