Here's a little tutorial to add your own picture to an Apple screensaver. I should note that it is much easier to do this by logging in as a root user, and then doing all of this via the Finder GUI. However I will include the way to do it with the Terminal here. (To log in as root, log out of your current user, then type in "root" as the username, and the root password as the password. Then follow steps 1-4.) I should also note that if you DO use the root user, you need to enable it via the NetInfo Manager application -- for instructions, just reply back, or pm me. I will also use the 'sudo' command instead of the 'su' command, so that you don't accidentally do something that you don't want to do (believe me, I've erased my whole OS X system folder with a single mistake and the hitting of a return).
Here you should find all of the built-in screensavers except for the Slide Show and Basic ones.
2. Choose the saver that you want to add pictures to: you can only add them to the Abstract, Beach, Cosmos, or Forest savers.
3. Highlight your choice, control-click on the saver's icon, and select 'Open Package Contents' in the contextual menu.
4. Open the folder called "Contents" in the window that appears. Then open the folder called "Resources". Inside here, you should see the jpg files that comprise the screen saver. At this point, you could just copy those files to the desktop and then just create a custom slide show. However, to add pictures, it's simply a matter of putting them in this folder and renaming them to the next number up (I didn't check to see if the name change was necessary). Note the naming system of the jpg files.
4b. For purposes of ease, it is easier to rename the files FIRST before moving them, if you're going to do it via the terminal. Looking at the naming system of the jpg files, name your files in the same way, starting with the lowest positive number that is not used. For example, if the last cosmos picture is named 'Cosmos10.jpg', then you should name your files 'Cosmos11.jpg', 'Cosmos12.jpg' etc., without the single quotes, of course.
5. Creating a custom slide show by using those pictures does not require using the Terminal.. just copy them to your desired target folder. However, moving items TO the folder DOES require root/terminal access. If you want to do this, open the terminal. Root access is actually easier because you can use the GUI this way to just drag them into the folder, and not having permissions problems. However, it's kind of annoying since you have to logout and relogin again (to log in as root, just log out, type "root" as the username, and the root password in the password field, and then just drag your files directly into this folder using the GUI, and then rename them to the needed filename).
6. Using the Terminal, keep the "Contents" window open (so you can see the icon to the "Resources" folder), and open the folder that has your desired pictures that you want to add to the screensaver.
7. You named all of your files that you want to place in the screensaver according to the naming system that Apple specified, right? Good. That will save you a lot of time:
Type 'sudo cp ' in the terminal (without the single quotes but with the trailing space), and then drag the Resources folder onto the terminal window. The path should automatically come up onto the terminal window. Type a space in the terminal window, and then drag the desired file you want to move into the Resources folder onto the terminal window. The path should also be entered automatically. DO NOT PRESS RETURN YET!! The command should look like this:
sudo mv pathtoresourcesfolder pathtodesiredfile
Note that the path to the resources folder and to the desired file will have spaces in them, but before each space there is a backslash. The backslash indicates that the space should be considered part of the path (not exactly, but it does that for the purposes of this tutorial).
Now, to make your life easier, we will make the transfer of all the files at once (make sure all of your pictures are in the same folder). Remember, you named all your files according to the naming system. So to transfer all of your files, replace the last part of the path to one of your pictures (for example, Cosmos11.jpg) with an asterisk replacing the part of the files' names that changes. For example, for the cosmosaver example, if you have 'Cosmos11.jpg', 'Cosmos12.jpg' and 'Cosmos13.jpg' to move, you would type 'Cosmos1*' instead. The * means anything in place of the asterisk, and so it copies all files that start with 'Cosmos1'. Note that any extraneous files that start with Cosmos1 may also be moved, so make sure there aren't any of those. The command should now look like:
This is just an example: your command will vary depending on which folder your pictures are in and which saver you are editing (remember that the backslashes negate the special function of the space).
8. Type return, and at the prompt, type the root password. If you type in the correct password, the files should be copied to the Resources folder.
That should be it. If it doesn't work, reply here, and I will try to figure out what I did wrong. I know it's kind of cryptic to go through the terminal, and I suggest using the root user if you can (see top and go through steps 1-4).
Hope that helped... maybe this should be moved to the how-to section!
Of course, in 10.1 you can ignore ALL of those instructions to use your own pictures in the screensaver.
In the screen-savers pane, just pick "slide show", then "configure"
Then, just browse to the folder you want to use, pick it, and VOILA!!