Planetbeing has released an app the allows you to change the bootscreen of your iPhone or iPod Touch (1st generation).
“This is a BETA release and hence is not officially hosted by any repository yet. You’ll have to install it manually.
This is a jailbreak only application (and hence is only available on the first gen iPod touch, iPhone 2G and iPhone 3G).
This is a pretty basic GUI wrapped around the core functionality. If you’d like more features, it would be cool if you showed your interest by making a small donation to me (firstname.lastname@example.org). Thanks!
Manual Install Instructions
1. Download: CLICK ME and scp it to your iPhone (e.g., at /var/root/LogoMe.deb)
2. As root, over SSH or Terminal.app, type in “apt-get install curl” if you don’t have libcurl installed.
3. As root, over SSH or Terminal.app, run “dpkg -i /var/root/LogoMe.deb”
4. You may have to restart SpringBoard or the iPhone for the app to show up on SpringBoard.
1. Connect to the Internet with your device (Wi-Fi or 3G or EDGE).
2. Open LogoMe.
3. Wait for some files to download (this only has to happen once).
4. Type in the URL of the boot logo you want on the second tab (for now, it has to be accessible on the web somewhere).
5. Optionally push the Preview button on the third tab (to see what it will look like before installing).
6. Push the Install Logo button on the third tab.
7. Restart your device.
Warning: If you ignore the warning about the logo being too big, you run the risk of having to restore your device. As a beta, not all the “guard-rails” have been put in.”
Remember that it is still in Beta but have had many success stories so far.
EDIT: Some people have had problems with their home button being disabled on firmware 2.1 and they had to restore to fix it. Be warned!