sharing photos and tunes
There are 2 options. If the two accounts are being used by 2 different people, they may want to have different photos or tunes in each of their music or photo libraries. In which case you just want to not have to duplicated the storage for your photos and music. There is a preference in each program to NOT copy the photos or songs into the library when adding them to iPhoto or iTunes. This way, you can keep your mp3 and jpg files somewhere on your hard drive or even an external hard drive and iPhoto and iTunes simply point to the songs and photos, thereby saving you the disk space. Each user then can select the photos and tunes they wish to keep in their iPhoto and iTunes library and make up their own Albums and Playlists. In addition, each user can offer to share their albums and playlists to others on the network.
The second option, if the two accounts are really for the same person and you simply need to have a different login for whatever reason and you just want iPhoto and iTunes to work the exact same way no matter which account you happen to be in, then you need to move their folders to a place that both users can access (like a Shared folder) and use what is called a symbolic link to put in effect an alias to the shared folder in each user's home folder to fool iPhoto and iTunes into thinking the folder is where they want to see it. iTunes lets you tell it where your iTunes folder is so you do not have to do the Symbolic Link trick to fool it.
There is a free utility that sets up a contextual menu (aka right click) to create a symbolic link. It is a much safer way to create an alias (aka Shortcut in Windows) under OS X than the Make Alias command (cmd-opt-drag) in the File menu.
<http://seiryu.home.comcast.net/symboliclinker.html>
Thanks to Nick Zitzmann for this handy utility.
HTH